Hirst Arts Help

[joe5mc]

Is anyone here (in the UK) using Hirst Arts molds. If so, can you let me know what plaster you use and where you get it? Everything I've found so far is very weak...

[Cait Sidhe]

Uh so I never got quite as far as using it... but the stuff I got for the purpose was StoneCast which I think is meant to be pretty strong

[Mammoth miniatures]

I don't use hirst arts BUT I do teach sculpture and use a hell of a lot of plaster. If you're using regular potters plaster then it should be strong enough for general game use, but it will be fragile. Remember that there is a balance with plaster - too much power will make a soft, weak mixture. too little and you'll get far too much shrinkage. ideally you want a 7:10 water to powder ratio with the consistency of double cream.

ordinary potters plaster can be strengthened by mixing PVA glue into the water prior to mixing. you can buy herculite and various other hard plasters from tiranti sculpture supplies/pottery crafts.
https://potterycrafts.co.uk/products/siniat-prestia-alpha-casting-plaster?_gl=1*k707mb*_up*MQ..*_ga*MTkzNzQzODgwNy4xNzQzNDU0NjQ1*_ga_RXSPQFFXNB*MTc0MzQ1NDY0NS4xLjEuMTc0MzQ1NDY1NC4wLjAuMA..#learn-more


Personally I'd recommend looking at jesmonite/water based acrylic resin. it's much much stronger and nicer to paint - It's the same material that fogou models use for their excellent terrain.
https://potterycrafts.co.uk/collections/jesmonite?_gl=1*4s6jur*_up*MQ..*_ga*MTkzNzQzODgwNy4xNzQzNDU0NjQ1*_ga_RXSPQFFXNB*MTc0MzQ1NDY0NS4xLjAuMTc0MzQ1NDY0NS4wLjAuMA..


As a stop gap you can also add fine sawdust into your plaster as a way to give it some much needed strength - mix the sawdust into your powder prior to adding it to the water.


EDIT: the other option is to use a polyurethane plaster additive - it replaces the water in your mix and makes the plaster FAR stronger. https://potterycrafts.co.uk/products/tiranti-acrylic-plaster-polymer?_gl=1*1wlozwl*_up*MQ..*_ga*MTkzNzQzODgwNy4xNzQzNDU0NjQ1*_ga_RXSPQFFXNB*MTc0MzQ1NDY0NS4xLjEuMTc0MzQ1NDkxNS4wLjAuMA..#learn-more

[fastolfrus]

last time I cast some was using Stonecast, but the best tip I got about it was to make sure it fully dried: including buying a cheap baking tray that I could put blocks on and stand them in the oven (after it was turned off but before it had fully cooled down from cooking). Then when fully dry glue together as required and paint before they absorb moisture from the air.

The results using the oven dried blocks compared to earlier (non-dried) bricks was very noticeable

[Pattus Magnus]

Whatever the plaster type, if you are not already doing it I recommend using a surfactant to help break the surface tension from water. It helps reduce bubbles forming on mould surfaces and ending up as features in the cast pieces. Spot remover fluid for use in dishwashers works as a surfactant.

There is information here: https://hirstarts.com/casting/advanced.html#wet

[Severian]

For various Hirst Arts projects, I've used Keramin which has lasted fairly well.

https://hobby.uk.com/keramin-1kg.html

[joe5mc]

Thanks guys, useful stuff.  I might give Keramin a try - thanks Severain!

[katie]

Not Hirst Arts but other moulds -- ScaleCast (O scale building parts and accessories -- think 1/45 scale linka), Diorama Debris (brick moulds, lintels, tiles and things in 35mm & 1/48), some generic block moulds off Ebay (mostly for structural parts), plus an ancient "Castlemasters" kit (very square bricks which are useful for structural work and some building decoration).

I use Herculite2 for casting all that.

I get it from "Neills Materials" in Bury St. Edmunds which happens to be handy for me. I can also recommend "Special Plasters" in Birmingham for midlanders. People near Newark might be able to get it direct from the manufacturer, British Gypsum.

It's worth buying it in larger more-economic quantities (I get 25kg a time) and I store it in airtight buckets bought off Amazon to keep it dry.

Wetting agent can just be a mix of 50/50 water and dishwasher rinse aid. I got some spray-bottles off Amazon for it. It makes a big difference getting corners and details out.

Make sure the moulds are well coated in it. I also put more water in than the recipes say - I do about 55ml/100g. The parts are good when they make a glassy "tink" when tapped together.

Recommend getting rubber bowls for mixing in. The dry remnants can be easily broken out when dry. I've also got some big plastic car "oil drip trays" to put the moulds in to do the casting. Firstly they can be tapped on with something lumpy to persuade air bubbles to rise and secondly they keep all the mess in one place. Hirst talks about "pounding" the table the moulds are on.

Also a plastic kitchen spatula for "scraping" the tops of the moulds. If you have the mix right there'll be a meniscus on the mould after pouring and when that goes all porridgey you can scrape it flat.

[Karadek]

Here's what Bruce recommended for ages. They even have molded bricks featured on the website.

<edit>I missed where you specified in the UK. Not sure what it'd be called over there.

https://garreco.com/merlins-magic-plaster/

[Daeothar]

I've been using dental plaster for many years; it's much harder than ordinary plaster of Paris. In fact, it's absolutely rock hard and you actually require tools to break or chip it. I even coloured it to look like concrete once, using pigment powders during BSC 2021: concrete road pieces.

I get mine from a local hobby store chain, which repackages it and sells it as 'dental plaster', so I don't know the actual trade name, but google for Dental Plaster and you're bound to get some hits.

[nickinsomerset]

Another question is what adhesive oil best to glue plaster?

[Ran The Cid]

I prefer wood glue for plaster bricks, but many of the thicker/tackier white glue versions will work well also.

[zemjw]

Hirst Arts building page - https://hirstarts.com/building/building.html

Aleene's Tacky glue is his favourite, but anything like that should work

[mikedemana]

I also have had good luck with Tacky Glue on Hirst Arts plaster bricks. In honor of that, my greatest ever scratch-build, a Saxon church using their bricks. And finally getting use in my Viking Town Raid game... 



Mike Demana