Wednesday, 11 June 2014

Casting miniature terrain with Hirst Art moulds and Plaster of Paris

When I was about 8 years old, my sisters and I would cast characters from 70s kids shows in Plaster of Paris. Years later, after I'd left home and was struggling to make ends meet, I used to make chess sets from dental plaster, paint them up, and sell them to tourists through a local shop window. I never dreamt then that a lifetime later (yikes, it literally has been over a lifetime later) I'd be mixing up white gloopy gunk and pouring it into little rubber moulds again!

As work continues with our electronic board game, we're starting to think about adding terrain and feature to demonstrate what can really be done with this system - we're pretty fired up about it; maybe it will change the way people play tabletop board games - but first we need to show what's possible. And nothing gets people interested better than an amazing looking set-up.

In fact, that's what drew us at first to the Hirst Arts moulds.

They're not cheap. They require a lot of work (and a lot of multiple casting) and even when you get everything made up, it still needs painting, shading, highlighting and all that. But as miniature board game terrain it looks pretty impressive. And we want our electronic board game to look impressive too.

A lot of people use the "classic" Space Hulk style of board game layout, and moulds to go with it:

In fact, we did the same with our earlier versions of the electronic board game

Some nice industrial edging would finish those board sections off a treat! But then we decided to stick to the original design, and to make a generic, rectangular-section-based gaming system. Which meant that layouts like this...

would eventually need to look more like this:

However, there's something quite appealing about a board layout with no gaps. Somehow it looks more "complete" - more like a claustrophobic sci-fi/spaceship environment. And the photo above is very reminiscent of the early version of Laser Squad (the game upon which we tried to base our own shooting-in-a-spaceship board game Starship Raiders).

We clubbed together and bought a couple of moulds from the Hirst Arts UK reseller - we went for number #301 and #320. We also got some dental plaster off eBay but because the moulds arrived before the plaster, we went to a local art shop and bought some Plaster of Paris, just to try them out.

Making up the models turned out to be quite fun. It was like being nine years old, all over again!

After receiving the moulds, the powder inside them was washed out thoroughly with washing-up liquid and a good blast of hot water. The Plaster of Paris was mixed up to a thick batter-like consistency.

We placed the mould onto a newspaper on top of a "lap tray" (one of those things with a bean bag on the underside that stops your dinner sliding about on your knee while you eat in front of the telly!). While pouring the plaster into the mould, we banged the tray, to help release any air bubbles trapped in the plaster.

After about five minutes or so, the plaster started to go like a toothpaste consistency. At this point we were supposed to scrape the top of the moulds with a paint scraper or palette knife.

Unfortunately, we forgot this bit, and as soon as the plaster was poured, we went out for some dinner and forgot all about them!

A few hours later and the plaster had set (at least, set well enough for us to turn the pieces out). The pieces came out really easily. Simply flex the mould back and lift out where each piece starts to come free of the mould.

For a first casting, the results were OK. Well, ok-ish.
The detail from the moulds came out nicely on the pieces - even the tiny mesh pattern on a grate covering came out quite sharply. But every piece had air bubbles cast into it somewhere.

The instructions said that the quality improves after the first few castings, so it seems that we shouldn't expect our first set to be flawless after all. Also, given we forgot to scrape the top of the mould, none of the pieces sit together nicely - the bases (and sometimes the sides) are all uneven and would need a lot of work to make useable. We'll put this cast down to experience....

On the Hirst Arts US website, under "advanced techniques" (which we ignored, since we classed ourselves quite firmly as "beginner") it mentions "wet water". This is simply water with an additive which breaks the surface tension. We tried the test they demonstrated - firstly, placing a drop of water onto the back of one of the moulds.

The water stayed in a firm, rounded bubble shape.
So we coated the rubber mould with some water mixed with about a tablespoon or more full of dishwasher rinse aid (the stuff that supposedly stops your glass from going streaky). The result was quite noticeable

This time the water ran and dribbled everywhere, uncontrollably. It seems that wet water does make quite a difference to how a liquid performs in the silicone rubber moulds. So we turned the moulds over, filled with the "wet water" solution, eased out any bubbles that formed - using a small paintbrush - and tried again.

This time the results were noticeably better. Compare the two castings above (the first ones are on the left, the second castings on the right).

In this photo (above) the later casting is on the left. The second castings were much better. Not completely perfect - a few of the tiny details still had pin-prick sized holes - but at least gave us some useable pieces, at least good enough to try painting up.

The downside to Plaster of Paris is that it makes quite fragile pieces (dental plaster, apparently, makes much more robust casts) but also the rather "loose" mixture we made (roughly 50/50 water to plaster) means these casts are likely to take a day or two to dry out fully. While they're set hard enough to be taken out of the moulds, they still feel cold and clammy to touch. Which suggests that they wouldn't take paint very well just now.

Luckily we're coming into the start of summer here on the south coast - maybe a few hours in the baking hot sun will help get them ready to paint, sometime tomorrow?

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