And again...

 
We used hair bands and rubber bands to keep the mold together. This worked but the resin over flow tends to ruin the hair bands by sticking in their fabric, where as it just breaks away from the rubber bands. I say we because it was Mette's idea to use hair bands.

Upon being poured, the resin tended to over flow very quickly. The entry vent needs to be much bigger.

Yesterdays resin mix cured within ten minutes, today's was only half cured after an hour. My analysis is, this is because the first part of the resin needs to be well shaken before being mixed with the second part. Since the resin cured so fast yesterday, I rushed today's test and consequently forgot to give part A a good shake before hand. My big problem now is how to clean the honey-like uncured resin residue from the mold. I'm hoping turpentine will do the job.

Some good news and bad news (as always)

Bad news: The first attempt at mixing the resin failed. It made a strange semi-congealed mess that never fully cured. I'm not sure what went wrong, but I assume I made an error when weighing and the ratio was not 50/50.
Good news: The second attempt at mixing the resin succeeded and made a small slab that looks a bit like cheese.
Bad news: I attempted to fill resin into the mold today. This failed for two reasons. First being the resin proved impossible to control when being poured. Second, the resin began to cure within minutes of being mixed and I never managed to fill even 10% of the mold.
Good news: the small amount of resin that made its way into the mold, captured those details of the model it came into contact with.

Yikes - Getting ready to begin casting

My poor blog has been utterly neglected of late, the reasons for this are many, but most are due to the near total freeze of my blogable interests. Since we moved and since Oleg died, I have barely done anything which didn't relate to moving out of the city, and/or my children. How this will manifest itself in the future I don't know, but I as am currently under employment, and working out of the house every day of the week, the freedom of being a free lance illustrator/unemployed bum is a thing of the past. Now I have the week ends and a few hours in the evening (which I usually waste by playing Battlefield 3).

My plan for this week end, involves the first attempt at casting a model tank however. I've bought and tested several liters of polueurethene resin from the UK, and the results were favourable. I also filled my mold with water to measure the amount of resin I need to mix but here I encountered a slight problem. The mold is quite heavy, and the water leaked easily if the mold was not held tightly together. Trial and error will have to determine how much pressure is necessary, but too much pressure risks warping the mold so I shall have to be cautious.

Mold making attempt number four

There hasn't been much to post recently, but now, finally, I have some progress worth blogging about. I have begun to make the mold for my 1920s assault tank (I have yet to think of a good name for it)

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The top three image show the model embedded in white clay and ready for the first layer of silicone. I chose to use clay this time around on the basis of a video I saw on You Tube, and because neither plasticene nor blu tack had been satisfactory. The tank is tilted in order to facilitate pouring the resin without trapping air bubbles. This is the biggest mold I have attempted to date. When finished it will weight approx 1200gr, which with the price of RTV silicone in Denmark, comes to about £146. 

Having poured the first layer, I compared it to the original maquette I made. Since it has the exact same dimensions, I could see the top of the model was only covered by about 5mm of silicone. This didn't seem much, though in theory it ought to suffice. I decided to play it safe and added another 200 gr of silicone.

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This is the current state of affairs. The silicon has cured nicely (it is fantastic stuff), and I have removed the clay. It took about an hour but as the clay is water soluble, it was easy to remove without doing any perceivable damage to themodel, though it has stained it slightly. I shall give it another wash tomorrow before I pour the second layer.

Yours truly, now with full protection, and music whilst I work!

Test nr 3 - another failure

The third casting experiment is now completed, this time with colouring added. The results were disapointing to say the least. Even before it was finished however, I had decided to terminate this line of investigation, since I had learned that I am essentially using the wrong kind of resin. I had noted the distinctive 'boat yard smell', and after a brief e-mail exchange with Mark Copplestone, I came to understand that I should be using polyurethane resin and not the polyester resin which I used thus far. When the third test reached the 25 minute mark, I opened the mold as instructed, only to find the resin was still loose. It came apart like gloopy yellow mud. I left it to dry over night but the damage was done.

Looking back at the first two tests, I find that they are still slightly sticky.

During the course of this project, it hasn't been easy figuring out which products to use. There are myriad types of silicone and resin and they are seldom marketed except under brand names. Hopefully, things will become clearer with time however

Polyurethane resin is said to be much better at holding details than polyester resin. It is also, apparently much easier to work with and isn't noted for its carcinogenic properties.

My next line of experimentation will take place once I've acquired some Polyurethane Resin and, possibly made a new mold. I'm slightly annoyed that I won't be seeing a squadron of assault tanks any time soon, but I'm being philosophical about it. Better to take it slow and steady than wade in quickly and make a mess of things.

There seems to be a conflict of culture at work here. Danish and Garman sites don't seem to want to sell to private individuals where as UK and US sites do. One German site I looked at typified the European attitude thus; "Most polyurethane casting resins are inflammable and hazardous to your health and the environment. For this reason, they are not allowed to be sold to private consumers. You will therefore be required to attach a copy of your business license or proof of your status as a professional when ordering this product."

Talk about conforming to stereotypes. 

Casting attempts one and two

The first cast, without any colour additive or filler. I screwed up with the first one and left it in the mold too long. I hadn't realised that I was supposed to take it out after 25 minutes. I thought that 25 minutes was the pot life, so it sat in the mold for 19 hours before I realised my mistake. I'm not sure but I think the excess heat caused the surface of the casting to wrinkle.
The tissue paper is due to the stickiness of the part, which also caught me by surprise when I removed it from the mold, and it stuck.

The first cast in outdoor light. Note the air bubbles. These are my biggest concern.

The second cast, with added stone filler. The resin/filler mix seemed to be much thicker than the clear resin mix I used in the first cast. It also took a much longer time to fill the mold. The wrinkles are gone, as this time I opened the mold after 25 minutes, but the air bubbles are still in evidence, despite my having knocked the mold and turned it about in the hope of dislodging the air.

The second cast in outdoor light.
I have ordered some colour pigments, and my third attempt will be with a resin/pigment mix. I'm not too impressed by the stone filler. 

First attempt underway...

My first casting attempt is now underway and a few observations spring to mind regarding resin.
I knew it was poisonous, and highly flammable, but I didn't realise just how corrosive it is. I mixed up 12 gr, for though I only needed half that I knew from experience that silicone sticks to vessel from which it is being poured, so I figured the resin would do the same and an extra 6gr should counter this. It did but it also ate through the plastic cup I was using to pour it.

The resin I am using is apparently designed to be mixed with various fillers. I have a 'stone texture' filler, but I decided not to use it this first time as I want to see what the resin looks like when it is 'raw'. You can also buy colours, and I'll probably invest in a colour at a later date.

The resin itself is not particularly fluid. Its viscousity and appearance are close to pourable honey.
When I began, I was wearing my air filters, but I realised that I could still smell the resin. It is similar in smell to fiberglass. I supposed my filters were not skin tight on account of my facial hair, and pulled the straps tighter, this seemed to work, though I now have a red chevron on my face

We'll see tomorrow if the casting worked or not...

Ready for the apocolypse

My air filter mask arrived, so now I'm, more or less ready begin resin casting. I just need to find the bottle of hardener I bought half a year ago, and read the instructions first...

Success! (I think)

Step one. I added two model parts, a command cupola and an external fuel tank, to a sprue.
 
Step two: I built the mold box using perspex.

 I wasn't sure how to proceed from this point because the instructions I was following called for the sprue to be placed in a bed of modelling clay, like plasticene or blu-tack and when I tried this, the pressures involved snapped the glued joints of the sprue. I decided to adopt a different approach and put a foot on the sprue so it could stand on a 1 cm bed of silicone.

Step three: Having laid a foundation of silicone, which I left to cure over night, the sprue was placed on top.

Step four. I needed keys, so I built a Lego frame and placed it along side the sprue.

Step five: I poured the second layer of silicone, making sure to be careful and avoid pouring the silicone over the model. This was quite difficult as the silicone is not an easy substance to control. I spilled quite a lot. I also found that my calculations were out by a good 25 grammes, and had to mix up a second batch in order for the silicone to reach the half way mark. Having completed this, I left it to cure over night again.

 Step six: After having applied the release agent (Dow Corning 7) to the second layer, being careful to make sure the keys were well coated, I poured the last layer of silicone and let it all sit over night. In the morning, I was pleased to find the mold came apart with a satisfactory squelching sound, and everything seems to be in order. You can see on the image how the accumulation of release agent in the keys has softened the edges of the lego bricks. It is noticable that inside the depressions made the model parts, there is no such softening.

My improvised mold making work station in the attic










My improvised gas mask - I've ordered a real filter mask, the chemicals are pretty nasty, but it hasn't arrived yet.

Another spectacular failure

Last night I mixed and added the second half to my second attempt at making a mold. Up until then, everything had gone according to plan, and I had managed to avoid the mistakes of my first attempt. Unfortunately the mold failed anyway. I haven't taken any pictures of the light tank model recently, so the above image shows it without many of the details which have been added since. The second mold was an attempt to replicate the track assembly, and very similar to the first attempt, except in that I used blu-tack instead of plasticene and the perspex box was smaller and closer in dimensions to those of the finished mold.

 In the next two images the blu-tack can clearly be seen below the first half of the silicon mold. Cure time was 6 hours, but I left the mold over night and didn't remove the blu-tack until 18 hours had passed. As can be seen in the image below, the blu-tack came away with relative ease and did very little damage to the model. At this point, things were looking good. I let the mold sit for another 10 hours then mixed the silicone and hardeing agent for the second half. I applied a generous spray of release agent as shown by the various tutorials I have read and seen and poured the mix last night.

I examined the result today and found a silicone brick. The release agent had done nothing to prevent the two halves from welding together so completely that even after I ripped the whole thing apart and examined it closely, I found no indication of anything like a seam.

In the image below; 1. shows the only damage sustained by the model. A few tracks came away during extraction showing how easy pvc plastic can be released from the silicone. 2. shows seepage points where the silicone had found minute gaps in the model. If the mold had been successful this 'flash' would have had to be removed with a scalpel before resin casting. 3. shows the location of the keys. Its noticable that the silicone was toughest at these two locations.

Having spoken to my brother since, I have decided to conduct tests using lego bricks until I perfect the alchemy involved. From my research, I hadn't anticipated this much difficulty. The process as described online, and shown on You Tube seemed pretty straight forward.

My first test will use talcum as a release agent (as advocated by an online tutorial I read), another will use hair spray (suggested by my friend Claus) and the third will use PTFE - Teflon/graphite locksmithing oil (suggested by my brother Peter).

The project continues!

Having put aside my Dutch army again (am now waiting for inspiration, more funds and a lull in 'tank production') I have returned to 'tank production' and started on my light tank's turret, which unlike the medium turrets, I shall not be relying on my brother to make in aluminium. Instead I built a frame using Evergreen PVC sheet (fantastic stuff but very difficult to get a hold of in Denmark. My entire stock is what the local architect's shop had left over in their stock room and they no longer carry the product as it is too expensive to ship from the USA. Once it runs out, I'm not sure whose product I shall be using) and filling it with Milliput (another great product). The idea now is to file and shape the turret until I get something that looks about right. As usual, I'm taking my inspiration from various British interwar vehicles.

The resin casting starter kit arrived from the UK this morning, and I opened it to find something of a surprise. For a starter kit, there isn't much in the way of instructions (luckily I have found this site to help me) and of the various parts of the product, one is (as yet) something of a mystery. Its called 'stone powder', and I'm not sure what its purpose is. It doesn't *seem* to be a necessary ingredient for casting in resin. I'm thinking that it may be something one adds for texture, as shown here. 

Below, are all the chemicals and paraphenalia I've bought so far. With the plastics, miliput, glues and other modelling parts, the total cost of the project so far is; 2,406kr ($417/£258). If I only have enough to cast the component parts for one model, that will make for a very high unit cost. My plan is to make at least seven seperate tanks, and make a master mold of each. How many I shall cast of each there after I don't know, but I'll want at least four medium tanks to face my Vickers Medium Mk IIs, and three light tanks to face my Vickers MK VIs. At my current rate of enthusiasm/production, this will take the better part of a year to finish.

My next step is to cut the perspex to make the box in which to make the mold for the medium tank's track assembly.

I'm also trying to think of some good catchy names for the first five tanks (designed to reflect the 1930's). They have to be 'tank like', but relatively neutral with regards to culture. So far, I have thought of dog breeds; Bulldog, Boxer, Terrier (would have to be the light tank), Mastif, Wolfhound, Greyhound, Harrier, Great Dane or Greek mythology; Atlas, Achilles, Heracles, Apollo, Ares, Titan, Hermes. Hermes would probably be the light tank I think. On the whole, I think I prefer the Greek names since they carry slightly more 'weight'. Oddly Roman gods just don't sound all that tank like to me.

Expensive frustrations

Its been a long hard month, full of sick children and their various needs and requirements. I've run a few RM games but not had the energy to do much blogging on that subject. Most of my spare time these days is taken up by my tank project or just vegging out with Battlefield 3. Now I'm down with fever too and I think Mette's getting it as well. Summer always seems to end with an onslaught of illnesses now. I suppose thats the consequence of parenthood.

In the meantime, I've just bought a few more Perry miniatures (four packs of unarmed pikes and a pack of skirmishers) and I'm hoping to find the time to start painting and basing my Sixteenth Century Dutch army (now 128 figures strong). To that end I went online to try (again) to find a book or two which might give some indication of colours, but so far I've not had much luck. On the Lead Adventure Forum some of the guys suggested 'Armies of the Sixteenth Century: The Armies of England, Scotland, Ireland, the United Provinces and the Spanish Netherlands 1487-1609' by Ian Heath, but pointed out how expensive this book is (it seems to sell every where for £100+. I went online and found a copy in the USA for £27 (inc P&P) and thought myself as proud as Punch... only to discover the day afterwards that the title was misleading and I had bought 'Armies of the Sixteenth Century; 2. The Armies of the Aztec and Inca Empires, other native peoples of the Americas, and the Conquistadores 145-1608', also by Ian Heath. Both books having the exact same cover of course and so leading to my confusion. To say I was disapointed is an understatement. I almost lost my self control and ordered the first book to the tune of £100. I didn't however, as I can't really justify (yet) that level of expenditure on a book that I only need to paint a few figures.
In the meantime, the Aztec book is winging its way across the Atlantic to me. I have no idea whether that purchase will inspire me towards new horizons or simply languish upon a book shelf here in my lair.

With regards to my tank casting project, I have reached a point of extreme difficulty. No one in Denmark seems to know what resin is. I have all the parts and pieces I need to make the master mold, but I can't cast anything because it seems no one in Denmark has ever heard of resin. I shall have to buy from the UK, but I am loath to do so as the postage costs will make the whole project that much more expensive. I bought the starter kit shown above (it cost £60 to get it to Denmark) and I'll use that for my first attempt (it is after all a starter kit), but after that, I hope to track down a supplier in Denmark for all my subsequent models. I'll add some more tank images soon.

Casting project update: 12 Ton Medium Tank

Here is a size comparision showing my '12 ton medium' tank model against Coppestone Castings' Vickers Mk II, upon which it is loosely based. The idea is, this tank model will share two turret variations with another model, both of which can be seen in my previous posts. For the pupose of this image, I balanced the running board on the track assembly, so its sitting rather low. It should be about 2mm higher up. Currently I'm working on the rear hull plate and trying to decide how to do the exhaust pipe which is meant to hang on the back. The question is, whether or not to add it to the hull or have it as a seperate element. If its stuck on the hull, it might prevent the finished casting from leaving the mold.

1930's turret designs

When I can find the time (and when I'm not being distracted by Battlefield 3) I'm still working on my medium tank casting project, and I've reached the post design stage for the turret. That is to say, I've drawn up my designs and am now ready for construction. My brother Peter (who is a precision engineer) has offered to help me by shaping some aluminium for the underlying structure, so I've made technical drawings of the two designs I have in mind. The project has two different hulls and two different turrets, and these can interchanged with each other, giving the possibility of three seperate tank models. The track assembly is the same for all variants.

Tank turrets in the 1930's came in all shapes and sizes. Since there hadn't been any major tank conflicts to influence design, many ideas which seemed good in theory were tried out. The most popular designs were cylindrical for obvious reasons, and hundreds of variants of the tapering cylinder or dome turret design were made. I've looked mainly to the Vickers designs for inspiration, since they produced so many prototypes in the mid war period.

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Above. From left to right; Light Tank Model 1936. Light amphibious tank A4 E12. Vickers Wolseley WT
Below; Vickers 6 ton light tank. A6 Medium Tank (not to be confused with the Medium Mk III). Vickers 'Independent' A1E1.

Casting project Nr 1 update

Its coming along nicely, though there are a lot of details I'd missed when I first thought this model through. The most important of which is the need to fill in all the holes since the model would not be able to exit the mold if I didn't... or at least I don't think it would. Having never done this before, I'm still a little unsure how casting actually works.

Casting project Nr 1

I'm teaching myself how to cast home made models in resin. My first model will be an anachronistic self-contained armoured vehicle track assembly that can be used on either side of a model. I'm using British inter-war vehicles as my primary source of inspiration. Casting project Nr 2 will be the body of the vehicle.

The master, as seen above, is made of PVC and milliput.