Saturday, 20 May 2017

Flames of War: The Black Brigade (Preview)

So its almost the end of May and I still haven't started posting blogs about my Black Brigade project yet.

Truth be told this project is a hell of a lot more involved than I ever expected it to be, all exacerbated by continual problems with the tins of Army Painter Matt Varnish I keep needing to buy and wait for and then a mass of time spent fiddling around with little bits and pieces that could just as easily be saved up and dealt with in one big batch.

Lack of discipline there!!!



Anyway in the interests of actually getting something posted I thought I would just give you guys a heads up on what it is I'm planning to do and then share a photo of where I am up to with the Black Brigade army I am waging war on!

So, I have recently spent a week in Poland and whilst I was there I was able to write a full biography of Stanislaw Maczek, the resolute and gifted leader of the Black Brigade in September '39 which I will be presenting in 7 separate blogs each dedicated to a part of his life. Each of these blogs will be accompanied by a separate blog which looks at in some detail one of the constituent formations of the Black Brigade, briefly looking at its history, combat record in September '39 and finished off with a part about the modelling of the formation being looked at. 

Finally in August I will do a post that is specifically dedicated to the uniforms of the 10th Motorised Cavalry and the Warsaw Armoured Motorised Brigades. I have long been of the opinion that the 10BK was clothed in Cavalry uniforms and with some minor modifications (such as head gear) this uniform remained barely changed by 1939, on top of which the September of 1939 was one of the driest on record and as such I find it almost ludicrous to suggest that the troops were fighting in their winter issue great coats which the majority of companies sculpt there figures in. Essentially what I am saying is that of you want to field the 10BK and absolutely insist on accuracy and variety, you are OK with a bit of modelling then you can use cavalry miniatures and use Peter Pig heads with German helmets and Polish berets. Anyway these are opinions I will prove or disprove in August when I finally receive some materials that will allow me take a close look for everyone who is interested.

In the meantime though, I just wanted to share a photo with you all.

Not a great photo, but it shows where I am up to with this gargantuan ball ache that is called the Black Brigade:



... so much still to do * Sob *

Still...

FIX BAYONETS!!!!!

Sunday, 30 April 2017

Flames of War: Sculpting the TKD

Well we are at the tail end of April now and I haven't yet posted a single blog (this one notwithstanding). Unusual for me these day, so anyway I thought I would see what I've got knocking about so I can at least get one out there.

This is what I've come up with:

Anybody who has even a vague familiarity with me will know that when I get my teeth into something I bite deep. Very deep.

I have to have everything and I have to know everything!

When I started buying all of my True North Polish so many years ago I thought I would just have some Infantry based forces and be satisfied with that BUT over the last 10 years my interest in Poland has not waned at all. In fact quite the opposite. Its now more of a raging obsession that just wont quit! The more I find out, the more I find that there is to find out.

A classic view of the TKD

One of these areas that just seems to keep on giving is the area of Polish idiosyncratic vehicle test beds. You will already have seen the two TKS-D tank destroyers that accompanied the 10BK on their long (or short as the case may be) struggle across southern Poland (a small modelling project that I am very proud of by the way) but what of their older sister concept vehicles? the TKD's?

Well as these are not technically Black Brigade they took a bit of a back seat, BUT as I hadn't posted much due to my work on the Black Brigade taking up a lot of my time I decided that now would be a good opportunity to finish them.

So...here is what its all about:

In 1931 the TK-3 tankette, a development of the Carden-Lloyd tankette was accepted for integration into the Polish army (in fact by 1931 most had been upgraded BUT the Black Brigade were still mostly using the original TK-3's). The Carden-Lloyd  tankette however, was also being displayed in a Self Propelled Gun version touting a short barrelled 47mm QF Vickers gun. This was like waving a pretty necklace in front of a Magpie where the Polish staff were concerned and once the Polish military had secured the rights to produce the TK series of vehicles under licence in Poland research and development of a self propelled gun version began in earnest. It was assumed that this gun carriage could be used as an artillery support vehicles that could keep up with the cavalry brigades as well as being deployed as an infantry support weapon.

A scale plan of the TKD

In 1932 the Army Engineer Research Institutes Armoured Weapons Construction Bureau in Warsaw, under the direction of J. Lapuszewski undertook the design task calling the project TKD

A colour profile view of a TKD as it would have been in 1939

The design of the vehicle was an open crew compartment with the sides providing only partial cover. The gun with its shield was mounted on the central axis of the vehicle and protruded over the front edge. Other than this the construction of the TKD was the same as it was for the TK tankette. A driver was positioned on the left of the vehicle, since the weight of the vehicle had increased the suspension was strengthened and the tracks widened.

A study of the front of one of the TKD's


The home designed and built experimental Pocisk 47mm wz.25 Infantry Gun was chosen to be placed into the TKD as there were no other suitable guns in Poland at the time. This was the first modern gun that was actually designed and built in Poland and was built in a short production run. They never entered mass production unfortunately as it was decided not to equip Polish infantry formations with specialist weapons and the armour penetration was not considered good enough. On a plus point however the weapon was equipped to fire high explosive rounds as well as armour piercing high explosive and canister ammunition. 

A study of the rear of the TKD

The gun itself, when mounted on the TKD had a vertical angle of -12 +23 degrees and a small horizontal angle to play with. The TKD also carried ammunition stocks of 55 rounds at full capacity.

Four of the produced weapons were taken to be put into the experimental chassis of the TKD's, although it seems that the 37mm SA.18 Puteaux (found in the turrets of the wz.29 Ursus and some of the wz.34 armoured cars) and the Vickers QF 47mm were also tested on one of the chassis' (vehicle no.1159) but there is no record of the results of these further tests.

Between May and June of 1932 four test vehicles, using chassis numbers 1156-1159 were completed using mild iron in all areas except the gun shield. This essentially meant that the test vehicles, other than the gun shield, were classified as unarmoured vehicles as mild iron could not resist kinetic impact to any appreciable degree.

After tests of the vehicles were completed the TKD's were formed into an experimental platoon and sent out to complete field trials. They were assigned to the anti tank squadrons of a cavalry brigade for the 1932 and the 1933 manoeuvres which showed that they met tactical requirements well.

The experimental TKD platoon photographed in the mid '30's with the Polish interwar camouflage scheme on display

The gun however had too weak armour penetration and was not in general supply in the army. Because of these things, and having no other weapon in the Polish army that would satisfy tactical requirements for the project it ended up falling by the wayside and being forgotten.

In the years to come the TKD prototypes were still deployed in the 11th Experimental Armoured Battalion in the Armoured Weapons Training Centre in Modlin.

In 1938 interest in the TKD started to gain a foothold again and the experimental platoon was assigned to the 10th Motorised Cavalry Brigade although there is some discrepancy as to whether the entire platoon of 4 TKD's were assigned with the 2 TKS-D's to the 10BK or only 2.

They were deployed with the 10BK for the autumn manoeuvres in August and September 1938 and then soon after took part in the deployment for the reoccupation of the Zoalzie province whilst the Nazis were busy dismembering Czechoslovakia. The province was taken over by the gunboat diplomacy of Jozef Beck.

One of the TKD's can be seen centre right behind the TKS-D in the foreground whilst on manoeuvres with 10BK

Further knowledge of the deployment of the TKD's is unknown. According to some unconfirmed information they took part in the defence of Warsaw in 1939 but what is known for sure is that they were no longer deployed with 10BK but were definitely used in a combat environment in 1939 although their combat capabilities were very limited by the fact that they were not in fact armoured vehicles.

An abandoned TKD with gun dismounted photographed by the Germans sometime in September '39

A view of the same TKD viewed from the rear with a column of Germans marching past.


Building the Beast!

If anything these were even more complicated to make than the TKS-D's because they were smaller, not benefiting from an elongated hull, and had a degree of increased complexity with regards to all of the hardware that was put into it.

The two finished model TKD's, each mounted on a small flames of war base

Unlike the enlarged crew of the TKS-D's the TKD only had a crew complement of 2 so I only had to find two crew members to put into these instead of the larger crews of the TKS-D's but one thing that held up the construction of these was that I had to find a suitable cannon that could represent the 47mm Pociusk that was used on them. After finding something I felt I could nip and tuck I still had to wait for it to arrive.

A closer look at the build

Once I had possession of the cannons I then had to work out a way to fix the modified version to the vehicle chassis and then design and sculpt the gun shield with its extreme angle folded over the top of the vehicle.

A square on front view of the build. Lots and LOTS of rivets!


As you will be able to see from the photographs I have used a mixture of brass, magic sculpt and styrene sheets in the overall construction of the models, including appropriating German vehicles crews and head swapping their heads with Peter Pig Polish beret heads.

A view showing some of the interior detailing required on these open top rust buckets with spud guns

The mudguards for the vehicle were made out of sheet brass cut into strips and then hand bent to provide the rounded front ends of the fenders and then bent between two pliers to create the flat edges bend at the rear of the fender

A side view showing how the fenders were made out of brass and formed using schematic contours

As I was somewhat of a pauper where it comes to ability in sculpting my track sections I simply ripped the track sections off of an existing TKS model that I had and simply made up some instant moulds with some of that Instant Mould stuff, I cant remember what its called BUT this worked great for the TKS-D's but by the time I came around to casting up some track sections for the TKD's the mould edges were starting to degrade quite heavily so I was starting to get soft casts. 

Another view of the TKD build showing some more of the internal detailing

However I reasoned that with the weathering that I am now doing on my Polish vehicles I can disguise these flaws quite easily!

A final view of the loveliness that is a TKD made of Styrene, Brass and Magic Sculpt!

Anyway, after such a long wait for my stuff to turn up that allowed me to forge ahead with these finally all of the necessary tasks were duly achieved and I finally had two TKD's finished and ready to take their place in the hallowed ranks of the Warsaw Armoured Motorised Brigade.

The next stuff you will be seeing from me will actually be Polish 10th Motorised Cavalry Brigade stuff... the Black Brigade!

...in the meantime...

Fix Bayonets!



Tuesday, 28 March 2017

Casting: The Black Brigade (Update)

OK ladies and gentlemen;

After three months work (quite literally!) I have finally finished sculpting, moulding and casting all of the 'must have' vehicles that I need to have for my Black Brigade... finally I can get back to painting!

So I thought I would give you guys a State of the World (of the Black Brigade) address so you can keep abreast of whats going on.

This is, as I have mentioned more than a few times previously, my first venture into casting so I whilst I was aiming for the best I was at least aware that the likely results would have unforeseen problems that I would have to address and overcome as I went.

Even using a vacuum chamber and pump air bubbles are a bitch that are a pain in the ass to resolve! Casting is actually prohibitively expensive, both in cost of materials and in the time that it takes to actually do. Principally because when you decide to do casting you cannot use the workspace for anything else concurrently because all of the bits and pieces that you need to use just kind of spreads. The cost of materials is surprisingly expensive, especially when talking about making the moulds. I had to use an entire months disposable income to purchase a 2kg kit and I've used about half of that already on these vehicles.

This isn't a project for the faint hearted...

Anyway, this is where I am with my Black Brigade at the moment:

The casting efforts to date
Just a quick view of all of my casting efforts to date. This image shows everything except a couple of misfires which I've kept around for use of parts.

2 full platoons of Vickers E type A and type B's
The thing that started this whole thing was a lack of decent sculpts of Vickers E tanks out there, this was the first vehicles sculpt I had ever done and I have to say, now that they are cast and ready to rock and roll, they must still be my favourites (with the possible exception of the C7P's)

You will notice that the machine gun turrets are metal, and that's because I couldn't be bothered to sculpt my own as I had so many spares laying around after making my 7TP jw platoons, I decided to use them as they were the same as the ones used on the Vickers E's in 1939. A convenient shortcut! 

...and these babies are pretty much bubble free!

C7P artillery and recovery tractors
Not strictly a vehicle that was used by the Black Brigade in 1939 they were however attached to the 121st Light Tank Company in 1938, and as I need to use them for other forces in my Polish army I thought I would post them here anyway. 

I doubt they will see much use BUT I'm so proud of my sculpting on this little baddass that I just couldn't pass an opportunity to show them off!

You can see that there are actually bubble cavities on these but they are small enough that they will be easily disguised and/or repaired by my reckoning.

Polski Fiat 508 Lazik staff cars and Polski Fiat 508/518 Light Artillery Tractors
 Here we can see the bare bodies of the Polish staff car (which will also be used for my Piechoty Company and Anti Aircraft platoons) and the light artillery tractor that hauled the anti tank guns for the Brigade.

I really struggled  with all of the light vehicles as if I pulled them out too soon the vehicles would deform so badly I wouldnt be able to reform them, and on some of them if I left them to cure for too long the fenders would be so brittle that when I pulled them out they would snap so I would have to time it properly to pull them out of their moulds whilst the curing was still in the Green Phase but quite advanced so that the cast still had a little flexibility. 

On the whole its worked out quite well and what bubble cavities there are can easily be filled although on the artillery tractors the tread board that comes forward from the rear wheel arch is a consistent problem with the casting and may take a little more brain energy to fix

Polski Fiat 508 Tczankas
I'm quite pleased with the motorised Tczanka's that I've run off. The forward radiator grill isn't quite where it should be but on the whole, and considering the abject lack of of images and schematics available for design I think I've produced something quite convincing.

You can see that the third one along has a few more defects than the others so I would say that I'm likely to attempt casting up more until I can get more of the quality of the first in the row.

Polski Fiat 508 Furgon's
These light utility vehicles were used to ferry around the HMG platoons and such like so I couldn't get away with not having them. They were the last to be done and took the longest of the light trucks because of the enclosed cab which I had quite a bit of wrangling with to get right (ish) LOL.

The castings of these were completed quite early and so have a lot of the initial casting flaws so although I've got four on display here I'm currently running a few more off so that I can see if I can get casting quality up to the last one that was cast (the first in the row above).

I'm also pretty sure that I've got a bit of scale creep on these so I may have to go back to the drawing board and increase the size of the wheels very slightly... more on that later! 

Polski Fiat 621L's soft backs
If there is one thing that the Black Brigade fields in spades its trucks and half tracks. All of these (to the tune of at least 24) need to have soft backs as I am not a fan of seeing military trucks with nothing in the back!!!

I need so many of these that I think Ill be casting these up long after I've finished casting everything else! Thankfully the design is simple with very little undercutting that could lead to mould tear and the mould is quite well built anyway!

Light Truck Wheels
As you can see from the above image I anticipate needing a load of wheels for the light trucks and staff cars so I made a couple of different designs and just kept running them off. 

I'm likely to need more as air bubbles in these are really a pain in the ass BUT with the right amount of prodding and poking with cocktail sticks usually gets rid of the problem!

Pneumatic Tyres
The Polish Motorised Artillery Regiments had all of the wheels on their guns replaced from spoked wheels to giant pneumatic tyres and whilst I have enough metal ones for my Light battery of 75's the 100mm Howitzer battery needs a lot of conversion both to the tyres and the gun shield so I decided to cast up some options!

Windshield frames
With so many light trucks and staff cars now in my Polish army there is a constant need for windshields so I created some light and flat moulds which I could pour micro amounts of Polyurethane Resin into... and THIS is the reason why I bought the Fast Casts Resin that I did. Because its capable of curing in really REALLY thin sheets which resin usually cannot do as the curing process relies on internally generated heat from the chemical reaction.

No problem here though!

Staff Car seats
...and finally we come to the last element that needs to be independently cast; the front seats for the Polski Fiat 508 Lazik staff cars.

Not much to say about these really!

So there we have it. This is where I'm up to. I'm still casting up extras just to see if I can improve the quality of the models that I will actually use although I don't see me doing that for much longer as I only need a few now.

I also haven't included the 4TP and 10TP tanks here as they are both quite complicated moulds and I need a bit more time to get my head around how I will resolve the casting issues due to the complex undercutting and heavy details around the cannon barrels...

More on that later though. In the meantime:

FIX BAYONETS!!!!

(I wonder if that will ever be cliched?) 

Monday, 27 March 2017

Casting: Casting the Miniatures

Finally we come to the actual casting of the miniatures. Everything has arrived. Nothing left to chance. I am finally in a position to start turning out the miniatures that will mean the difference between a Polish 10th Motorised Brigade comprising anything but the equipment that they actually used and a Polish 10th Motorised Brigade that is historically accurate portraying the gear that they were tooled with. All I had to do was take the plunge!
...
Just me and my tools! (You know what they say about bad workmen and their tools right?)

All the moulds are made and I was ready to rock and roll... and I just so happened to have a day off from my job which is taking altogether far too much time from my hobbies these days. I tucked in my bottom lip and struck out.

Now, I have read a LOT about casting and as such I felt that I was pretty well informed. I thought I would know how to overcome the problems before they occurred and bought into my own bullshit that I would be able to produce work of an outstanding quality

How wrong I was!.. but more on that later.

First thing that I decided to do was to lay out my work-space in such a way that I would have everything to hand quickly. 

When you are mixing polyurethane resin, the pot life (i.e how long it is usable in its mixing vessel) is only a couple of minutes long so you need to be quick. By a couple of minutes I mean that 2-3 minutes is considered standard. I opted to have a Long Part B which would give me a pot life of between 5-7 minutes. The is very misleading however. The pot life includes the time that its pourable consistency is akin to thick treacle which for what we are doing would prove useless.

The beginning consistency of the Polyurethane Resin that I've chosen (TOMPS Fast Cast Polyurethane Resin) is more like milk which is perfect for miniature casting because you can start by slush casting the inside of your mould, thereby ensuring that the resin touches and sticks to all of the undercuts and fine detailing on your miniature.

If the resin thickens too much this will become impossible and you will be left with gaping holes in your miniature when you extract it from your mould.

The first thing that I did was place my disposable cup onto my electronic scales and turn the scales on, which gives a beginning reading of 0g


The set up of the casting workspace. Moulds to the left, resin at top and mixing pot and scales in the middle... complete with disposable chopstick stirring rod.
Its a well known fact that Polyurethane Resin is sensitive to its mixing ratios which if you get it wrong can lead to vehicles that either never cure or sweat once cured. Neither of which is a result that you want. When I received my Polyurethane Resin Part A and Part B I was quick to notice that there seemed to be a lot more of Part B than there was of Part A and this is because the instructions for use are very specific about using a 1:1 ratio of Part A to Part B by weight... which is why I have electronic scales in the picture. 

34g of Part B in the disposable mixing container.
When I first started I decided on mixing up a big batch that I would use for all of my moulds and duly when about measuring a large amount (about 70g worth) of Polyurethane Resin by adding Part A to Part B which was already in the cup. I proceeded to give it a thorough stir and it was indeed the consistency of milk which I was happy about. Then it went into the degasser to degas it.

Pointless exercise! The milky consistency means that air bubbles are not generally caught in the cup so this was effectively wasted time.

However after about 30 seconds in the degasser I whipped it out and started to pour it into my moulds quickly. Once full the moulds were put back into the degasser so that it could do its work on the rapidly thickening resin.

A very bad picture of the moulds being degassed. Lots of net curtain reflections :D

This was worth the time! There were bags of air bubbles being pulled out of the mould and after a couple of minutes I pulled out the moulds from the Vacuum Chamber and left them to cure on the desk.

The first moulds sitting on the desk waiting for the resin to cure.
The demould time for this resin is supposed to be 30 minutes. Bear in mind however that the smaller and thinner the piece to be removed from the mould the longer that the curing process will take. This is something that I had failed to take into consideration... to my cost!

After a half hour or so had elapsed I started to remove the castings from their moulds. The largest of the moulded vehicles were solid enough, although if pressed and twisted hard enough would deform. This is called being in the Green Stage which is where a casting is solid but still retains some slight flexibility. With vehicles that have intricate parts such as fenders and like this flexibility post demoulding becomes extremely valuable as you are able to move things around slightly.

The smaller vehicles such as the Polski Fiat 508's were still far too soft to be removed and so had to be reput back into shape and left. As it happens, with the correct mixing of the Polyurethane Resin these smaller vehicles take about an hour to cure hard enough to remove from the moulds without being destroyed. At about an hour the vehicles are still in their Green Stage so retain some limited flexibility.

The first vehicles being released from their moulds
Now, it has to be said that on removing the vehicles from their moulds I was mighty pleased with what I had achieved, and that pleasure over rode all of the flaws which jump out at you. It turns out that despite having a de-gasser there are things that I must have not done effectively enough because as you can see from examining the C7P and the Polski Fiat 508 Furgon there are small cavities all over the miniature meaning that there were air bubbles trapped all over the place

My first C7P  still on its resin funnel which needs to be cut away, and showing all of the cavities.
The first C7P had its flaws. There were plenty of cavities all over it BUT the issues were small enough and localised enough (predominantly in the area of the tracks) that I am rather of the belief that most of them can be fixed with putty filler and failing that when painting I can weather the vehicle and plaster it with MIG's mud to disguise the casting errors. 

The first Polski Fiat 508 Furgon showing the fender cavities

Another view of the Furgon from above showing the fender cavities
I've spent the whole day casting now and I've had plenty of opportunity to try different things to see what works and what doesn't.

I have to say that I feel that I have it nailed now. The vehicles no longer have any air bubble cavities, cure well and look good.

I decided soon after my first attempt that I would need to mix up smaller amounts of Polyurethane Resin and pour just into one or two moulds at a time. This meant that I would be able to make use of the milky consistency of the resin to get into all of the mould details and wouldn't have to wrestle with a rapidly thickening sludge!

I no longer pour the mould full straight away. There are parts of each mould where air collects and in order to get rid of these air bubbles I only initially put a small amount of resin in and massage the resin into the mould extremities by twisting and turning, pushing and pulling the mould. This isn't fool proof but it does make a massive difference. This is especially useful when doing stuff like turrets and you need to get the resin down the gun barrels.

Once the resin has invaded all nooks and crannies I will then pour the mould full and place into the vacuum chamber and switch the pump on. I make sure that I leave it a good while now on. I don't mind the resin curing inside the chamber for as long as its in there unless there are a mass of air bubbles that are pulling the resin over the lip of the mould. In this instance I keep thumbing the air tap on the vacuum pump on and off to tease the air out.

Again this isn't fool proof but the vacuum pump does 90% of the work, with me providing a bit of manual vibration giving the last 10%!

...

And this ladies is the quality of what I am getting now:

A brand spanking new Vickers E tank. No defects, no air bubbles... just lots of Polish goodness! 

This is a casting of a Vickers E that I have done towards the end of my current learning curve. There are no air bubbles on the casting and the detailing is accurate and high, Now I just need to do another 9 of these!

I'll do an update post when I have cast all of the resin vehicles for the Black Brigade so that you can see whats going on OK?

Whats that?

Fix BAYONETS!!!!!














Thursday, 23 March 2017

Casting: Making the mould

Well I promised you guys that I would walk you through my learning process as I attempt casting models to a level of quality that I would be proud to sell to my fellow modellers and gamers.

Nothing professional here, but more a desire to have decent looking models as opposed to whats out there and available for the Black Brigade. 

So we have already had a look at the gear list that I have had to put together in order to be able to start knocking out all of this stuff that I need. Its now time to start using it.

First stop was the vacuum pump, and I have to say that this was a real ball ache.

The Vacuum Pump

The Pump that I bought must have been an end of line piece of gear as they don't manufacture it any more and it is absolutely impossible to find instructions on how to use it online. All I have is a German language instruction booklet that was produced in China and was delivered with it!

Thankfully my significant other is fluent in German

Any excuse to get some exposure! She made me do it!!! :D
However, the diagrams do not point out vital elements on the schematics and the German descriptions turn out to have a generous spattering of Polish in them as well.

Poor show!

After wrestling with it for an hour or so I FINALLY worked out where to put the oil into... and had to spend an hour and a half pouring oil into it! I ended up resorting to a micro funnel with a cocktail stick stuck down the middle of it to get the oil into the pump without air bubbles causing constant spillage! 

WHAT A BITCH!!!! No wonder they don't make it any longer! Incidentally all of the other ones that you see now online all have Oil Intake Ports on the top of the pump so my problem will no longer be anybody elses!

After testing the pump to make sure it did what it says on the tin (so to speak) the next step was to prepare the prototype for making a mould around it.

I've chosen to do the soft back for the Polski Fiat 621 truck. The reason for this choice is that its a simple exercise in learning a process. Very little undercutting and not much surface detail that isn't bass relief. Should be something easy to pull off... and as I need so many of them anyway I thought it would be a good place to start.

This process is called Drop Moulding and is probably the most simple of Moulding processes. Simply put you just drop liquid Silicon over the prototype in order to create the mould. 

The very first thing that needs to be done is to measure up a base board and trial fit a Lego retaining wall to the board which will create the receptacle for pouring the silicon into which will actually create the mould.

Once the board is measured up cut it with a healthy border surrounding the Lego.  Its important that the mould base board can fit inside the Vacuum cylinder otherwise you wont be able to degas the mould.


Once everything is measured up the first thing to do is to glue the Lego bricks to the base board so that there is no chance of any of the Silicon bleeding through under them and ruining the mould. To make it easier for the Glue Gun to reach the bottom of the bricks only use two layers of bricks initially.


The next step is to but a Blue Tack 'funnel' onto the bottom of the piece to be moulded. This Blue Tack fills three functions. Firstly, it creates a tight seal of the item to its baseboard so the mould integrity is not compromised by creating flashes and invasions of silicon where you do not want them to be. Secondly this Blue Tack actually creates the 'funnel' through which you will ultimately pour your resin when you are casting new copies. Thirdly this 'funnel' creates a receptacle for extra polyurethane resin which, when you degas each new casting, will provide enough extra resin to ensure a perfect casting when the elimination of the gas bubbles within the casting depletes the extra resin as it takes the place of the bubbles. 


Depending on the viscosity of the resin this may be a negligible amount BUT personally I would rather have more than not enough to cover this possibility.

The next thing to do is to press this Blue Tack funnel to the Moulding Base Board to ensure that there is a tight seal all the way around to prevent silicon leakage.


The final step in the preparation of the mould is to build up the Lego retaining wall to a level that is higher than the piece to be moulded ensuring that it is high enough that the mould will have a solid and sturdy base once the silicon is cured.


...and there you have it. The Mould is now ready for its silicon to be poured in.

... and that's where everything became touch and go!

So having finally received my two giant syringes (which I believe in a former life may have been used to impregnate Diplodocus' in Jurassic Park!) I allocated one syringe for the Catalyst and one for the base of the Silicon. So long as they are only used on what they are labelled for the liquid will never cure and so the syringes will be reusable.

Now this silicon is supposed to be extremely fluid, which is the main reason that I bought it BUT when I drew it up into the syringes (same for both parts) it was as liquid as Golden Treacle! That's thicker than Maple Syrup to all of you Yankees and Cannucks out there ;) This worried me a bit as with all of the undercuts on these models I thought that this may present a serious problem as I attempted to make these moulds.

I drew up 80ml of each of the two liquids and deposited them into a mixing pot. This Silicon is addition cured which means, amongst other things, that you can measure it by either weight or volume so long as its a 1:1 mix. Happy days! I gave it a good stir in its mixing pot and then put it into my vacuum chamber to be degassed. Thankfully as I stirred it around it also became more fluid as well so it may not come with the casting issues that I was stressing about.

Now, this is the first time I have ever used a vacuum pump in anger so the results were perhaps predictable. I sealed the chamber and switched on the pump...then sat there watching the pretty air bubbles rising to the surface of the silicon. I bled the air out periodically and then when I decided I had done enough degassing I did a final opening of the air valve... unfortunately I opened it immediately and completely not knowing that it would also bleed air into the cylinder straight down into the silicon... which exploded all over the vacuum cylinder! Doh!!!

Silicon Explosion after catastrophic re-gas!

Thankfully I had made enough to still complete my task so I took it out and poured it into the mould wall containing the prototype. Still pretty viscous but I angled the mould and poured slowly into the bottom corner allowing the silicon level to rise under the undercuts of the prototype levelling the mould to the horizontal only when the silicon was in danger of spilling over the top.

Mould after the initial pour and before degassing.
Once the mould was filled I could see that there were an incredible amount of air bubbles still in the silicon so I decided to put the whole mould into the vacuum chamber.

This time instead of degassing and re-gassing cyclically I decided to leave the pump on for a good thirty seconds or so until all of the air bubbles had been drawn to the surface only bleeding air into the chamber slowly and only when it looked like the silicon would pour over the surface of the bricks.

Degassing the mould. You can see the remains of the silicon explosion to the right.
When I finished degassing I took the mould out and noticed that the majority of the air bubbles (of which there were millions!) that were left were laying on and just under the surface of the mould and so wouldn't affect the integrity of the mould detailing so I was happy about this at least.

I also realised that I probably had enough silicon left in the pot to do another small mould and so I knocked up a mould for my Polski Fiat 508 Lazik Staff Car as well, and went through the same process with one exception. I stopped feathering the gas tap and just let the chamber do its work for longer periods. The results were much MUCH better!

Both moulds being left to cure after degassing.
Something else that became obvious after I sat there watching the moulds cure was that despite the silicon being extremely viscous the air bubbles that are initially trapped in it will still slowly rise to the surface and burst. I wouldn't want to bet my mould detail integrity on this though because any excuse at all to trap an air bubble will be taken I think BUT it is a help.

The state of the moulds after an hour.
Looking at the photo above we can see that whilst the initial mould still has plenty of gas bubbles the smaller of two moulds, the second mould has almost none, and those bubbles that are there are all tiny and near the surface.

On the silicon tins it says that the de-mould time is 2.5 - 3 hours although I will probably play it safe and just leave the moulds until tomorrow before I remove them.

...

Well after three hours the silicon was nowhere near cured, in fact it was only just reaching the 'tacky' stage. This did cause me some concern as I left for work wondering whether or not the moulds would cure at all.

Flash forwards to 6am and I arrive back home to find some beautifully cured moulds with absolutely no air bubbles inside the silicon at all.

The two finished and cured moulds, labelled, with the prototypes next to them
The prototypes were surprisingly easy to release from the mould. Looking inside the mould I couldn't find any evidence of air bubbles spoiling any of the detail either so I can say at this point that I would consider this to be a successful first venture into the heady world of casting miniatures.

A look at the detail inside of the mould
So, the next thing to do would be the actual casting of these miniatures BUT instead of that I'm going to spend a couple of days making all of the moulds that I will need for all of the vehicles that I'm going to be casting up so that if I am over ambitious with the amount of resin I'm mixing up I will have extra moulds in which I can pour it so that it doesn't go to waste.

I'll do another blog on the actual casting of the products soon but for now...

Lessons and Observations

i) When using the vacuum pump don't keep removing and adding gas into the chamber. Switch it on and leave it on to allow it to do its work, only adding gas back into the chamber IF the silicon looks like it will flood over the top of the mould retaining wall.
ii) The Lego retaining walls should be twice the height of the pour level of the silicon if degassing is to be attempted to prevent the silicon flooding over the top of the walls.
iii) Even though the retaining walls are glued to the base and the bricks fit tightly against each other the vacuum chamber will pull silicon through the joints between bricks and base. It isn't a problem as its such a small amount but it does still happen. This is one of the reasons why you still need your border around the wall.

Now, when all is said and done... FIX BAYONETS!!!!