Sunday, 22 February 2009

Mould Making

This week I’m going to have a look at using mould making materials to aid your terrain making and modelling. But first, a round up of what’s been going on.

Weekly Update
No gaming this week, due to work commitments, so I’ve been on Board Game Geek (BGG) trying to track down somebody who want’s to trade their copy of Blood Bowl. I really fancy getting into BB and I’m looking at downloading the living rule book from Games Workshop, but by the time, I’ve made the board and markers, bought teams and all the extras, it could well be worth just getting the boxset! BGG has a facility where users can list games that they want to trade away and list games they want in return. Unfortunately BB is a big game and most of the current owners live in the US, meaning that postage is prohibitive at present. If you live in the UK and have a copy of BB you fancy trading, check me out on BGG and perhaps we could arrange a trade.

I also had some very good Frugal Gaming news this week, I’m not going to reveal it yet, but expect to be reasonably impressed in a few weeks (I was!).

Matt and I have started work on a modular board for Necromunda, It’s based on 6mm thick MDF cut into 30cm squares, each piece will have a bit of terrain on and they can then be fitted together in a number of configurations to make a playing surface. We’ve had a sunday afternoon getting started on them on we’ve got a couple currently under construction. They’re looking pretty good so far. I’ll give them a write up in a future post, but it leads me nicely onto the subject of moulding and casting...

Mould Making
I’ve always enjoyed the modeling aspect of the wargaming hobby and I love making terrain pieces for games. A couple of years ago I wanted to make some rubble piles for Necromunda and decided it might be worth casting my own pieces. After a bit of research I came up with two options:

Latex Moulding - You’ve most likely seen latex moulds in children’s plaster of paris casting kits. They are very flexible and don’t show much detail. I’ve never created latex moulds before, but from what I’ve seen, they’re pretty easy to make. After creating your master model, simply paint on a thin layer of liquid latex and allow it to dry, you can then repeat this procedure to get the layer to the thickness desired. Obviously the thicker the latex, the more durable the mould is, but the longer it’ll take you to make it. You can buy thickening agents to speed up the process, though I’m not sure how effective they are. The benefits of latex are it’s low price and ease of use, though the lack of detail in the final mould puts a lot of people off.

RTV Silicon - RTV stands for Room Temperature Vulcanising, which basically means that you don’t have to heat the solution to get it to set. This type of mould material is more difficult to work with and is generally more expensive to buy but it gives massively improved results. It comes in two parts; the silicon and a catalyst which are mixed by weight. The catalyst is generally only added in small amounts compared to the silicon and must be mixed in thoroughly. This mix is then poured over the master (surrounded by a suitable barrier to stop it going everywhere) and then allowed to set, generally, this takes over 18 hours. The mold is then removed and casts made as normal.


I think we’re getting ahead of ourselves here. The first step in mould making is to create the master that you’ll be making the mould from. It’s really important to get this right and there are lots of things that you can do wrong and ruin your mould. But fear not, it’s all common sense really, just don’t create any hollows that are larger than their openings (so no bulging, hollow cauldrons), and don’t create any holes that will mean you can’t release your mould (so no handles on crates).

As part of the terrain that Matt and I are making we wanted lots of buildings. We were particularly impressed by the Cities of Death terrain by Games Workshop, but weren’t prepared to spend a couple of hundred pounds to fill a table. Matt asked if I would be able to create something similar for a more realistic price and I took up the challenge.

I came up with the idea of a foamcard shell with moulded plaster pieces stuck on to add detail. This meant I had to produce lots of little decorative architectural pieces such as columns, vents and plaques. I made these from 0.7mm plasticard in layers with further detail added in ‘green stuff’.

Once these were done I could start the mould making. I glued all the pieces I had made onto a grid on a piece of scrap MDF I had and surrounded it with a 25mm high wall of plasticard to stop the silicon escaping before it set. I then used my glue gun to seal up all the little cracks between the piece of plasticard wall as the silicon will leak out of even the tiniest hole.


I then roughly calculated how much silicon I would need (based on the volume within the plasticard wall and mixed the required amount of silicon in an old tin can.
This was then poured over the mould, using an old brush to make sure the silicon got into all the detail in the master.


This was left for 24 hours to set before I removed the frame and carefully peeled the mould off the master.

I am now the proud owner of a silicon mould that I can use to make architectural details for a wide variety of models. In fact I decided to make another mould using the same master, so that I can cast two sets of pieces simultaneously, doubling my output!

All this sounds very good, but is it frugal? At first glance no. The silicon costs £18 so if you’re only making a single model or a couple of models then it’s not worth it. But if you need to fill a table with buildings or terrain pieces all using similar elements, then this is a fantastic way to do it. As I said earlier in the post; high quality building models, as produced by Games Workshop and other firms, are quite pricey, so there’s a big margin for saving money and getting the same kind of quality. But it can be a big outlay so make sure you’ll get the best out of it before you decide to try it.

The first Necromunda buildings are slowly taking shape, but there’s a lot of work still to do. When a couple are complete, I’ll post a full report, showing exactly what we did and how we used the moulded pieces.

I hope you enjoyed this quick introduction to mould making, If you have any questions or suggestions, please post a comment below or send me an email. Happy Gaming.

9 comments:

Ruarigh said...

Excellent tips on the mould making. I have been meaning to make moulds for my Egyptian terrain to speed up production but have never worked up the courage to risk getting it wrong! I look forward to reading the new frugal gaming news too. Please don't tease us too long!!

Dave said...

He he! Thanks Ruarigh. Expect to mke a few mistakes when making your first couple of moulds. My main problem was not sealing the barriers properly and getting the material everywhere. If you need to get a lot of pieces made, it's certainly worth a try...

Chicago Terrain Factory said...

The savings point on mold making/resin casting comes from moving from the sample size to buying by the gallon. Cost per unit drops by a factor of two or three times. Problem is - you need a project big enough to use a gallon of resin.

Sentient Bean said...

Nice article!

One suggestion: I used to use similar RTV years ago and it cured in about 12 hours or so.

I've since changed to a RTV silicon sold as "Pinkysil" in Australia which is stronger, carries more detail, is a little cheaper and CURES IN 20 MINUTES!

Bin that blue stuff and try and track down Pinkysil.

Dave said...

20 minutes! That's sheer madness. I've never heard of that brand before. I may have a look at that for future work.

Thanks for the tip.

Chicago Terrain Factory said...

I'd be worried by any RTV that sets in 20 minutes - that's as fast as some resins set up. One of the advantages of a slow setting RTV is de-gassing. With a 20 minute set time, the only way to get bubble free molds would be with a vacuum and/or pressure chamber.

Chris Tregenza said...

Just letting you know that this post (and another one) has been included in this weeks round up of best miniature related blogging: Lead Bucket

Sentient Bean said...

Fear not, Chicago Terrain Factory..

It's held up longer than my old blue molds And zero bubbles thus far with my one piece molds. Please don't make assumptions until you've actually had a look at the product data or used it. :)

Oh, and it's the same price as the old blue stuff, too.

Google "Barnes casting supplies" or some variation to find the website with all of the product information (strength,etc).

I'm sure it has some drawbacks, but for what we're doing, the detail level is amazing and I would never go back to the 8-20 hour stuff if you paid me.

Jesse said...

You can also use 100% silicon caulk - such as for windows or bathrooms - as a mold medium. I use GE #1 here in the U.S., which runs about $5 a tube; one tube should be adequate for almost any miniatures casting project.

There are two key things to remember: First, it _must_ be 100% silicon, otherwise it won't cure properly.

Second, you can't just squeeze it onto the original. You need to squeeze it into a strong solution of water and dishsoap (such as Dawn or Joy) first. This gives you a protective coating that prevents the caulk from sticking to the original (or your hands!). Then you grab the extruded caulk from the soap basin and mold it onto the original with your hands, being careful to avoid air bubbles and such. You'll have about ten to fifteen minutes from when you squeezed it into the water before the caulk cures too much to be effective.

It takes about 24 hours to cure; technically, it cures faster than that, but it'll stink like vinegar (acetic acid) for at least that long, so let it cure somewhere well-ventilated. It picks up detail quite well, at least in my experience.

Should you decide to try silicon caulk mold making, TEST EVERYTHING FIRST. That way you can be sure you have the right soap solution, the right caulk, and that it'll work for your purposes.

In short, it's a messy but cheap, widely available, and durable alternative to "real" casting products.