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"Newbie advice on casting?" Topic

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Mingans Marauders Inactive Member14 Apr 2015 2:21 a.m. PST

I've been cutting plastic card to a certain pattern for awhile now to make custom bases, but its starting to become a pain. Recently a friend has talked me into doing casting, but we are both mostly completely new to it. We have a few friends who have cast in the past, but all seem to have a different method/idea of how to do it and I've seen barely anything they've done.. I've tried to read what I can and watched a few videos, but I wanted to get some advice from everyone here.

I've heard a lot about hydrocal, but it seems to be in different forms. Which kind is the best to use for bases? Apperently you can find it at certain stores as "Gypsum Plaster", but do they come in various grades? I read to stay away from the Woodland Scenic version, is this correct?

I've also read on Hirst Art about Die Stone with three brands coming up, Merlin's Magic, Excalibur, and Die-Keen. Again does anyone have experience with working with these materials to build miniature related items?

Somewhere it was talked about using the Durham Rock Hard in those Woodland Scenic rock molds, could it also be used as a material to cast bases with?

The idea of a vacuum form was thrown around a lot by one of our friends, but would the trouble and time be worth it for casing bases? Once we get used to doing the bases our goal is to work on other items that use two part molds, I'm guessing that's when the vacuum form would be most useful?

We plan to use resin on the two part molds(mostly its larger figures we've sculpted), but I'm trying to find something that will be a semi cheap alternative to resin for the bases and possibly certain terrain items. Is it maybe just best to stick with the resin and skip trying to use those other materials?

On the subject of the two part molds, I know of two methods. One involves pouring the mold over the model with a channel piece somewhere on it, then with a sharp knife cutting a slit on the mold to remove the figure and then later the cast piece. The other is placing the model into clay half way, pouring the mold, removing the clay and pouring the other half. Which is the best method? Or do both work, just it depend more on what we are trying to mold?

I should note the bases are typical 25mm, 30mm round lip and so on and so fourth. And the pattern is a flagstone, with some other things we've been coming up with that is sort of a urban rubble(bricks stacked up and such).

Thank you for any advice, I really appreciate the help.

Mako11 Supporting Member of TMP Inactive Member14 Apr 2015 2:39 a.m. PST

I'd just use a one-part mold, if you are making bases.

Why over-complicate it?

No need for a two-part mold, really.

Not sure, but some of the new putties and plasters are supposedly pretty durable.

Urethane resin is quite durable, but is expensive.

Lonkka1Actual14 Apr 2015 2:45 a.m. PST

CoolMiniOrNot have Instant Mold available.

Warm it up in hot water, make a mold by pressing it on your base and use it as a press mold with green stuff and the like.


Ran The Cid14 Apr 2015 4:33 a.m. PST

A one sided mold is all that's needed for bases. Use a plastic scraper to remove any excess casting material. I recommend casting in resin – a $35 USD sample size will provide more than enough resin for the project. Plaster will be noticeably heavier and prone to chipping, and not all that cheaper at this scale.

Here are my notes on base casting: link

Personal logo Sgt Slag Supporting Member of TMP14 Apr 2015 9:41 a.m. PST

You can also make a press-mold, as mentioned, but use polyforma clay for the bases: Super-Sculpey and others, are readily available.

With regards to two-part molds, you DO NOT want to pour the mold agent on top of the master… This will create air bubbles galore! Instead, use a disposable brush, and brush the mold material onto the figure, carefully applying it to the deeper cuts and folds of the master. Once this is done, and cured, apply additional layers, in a thicker manner, possibly pouring the mold material onto the brushed-on layers, but make sure the brushed on layers are not thin, as pouring the mold agent can still form bubbles, which will weaken the mold.

High Temperature RTV Silicone can be purchased from any automotive supply store. This is the material a friend used for making molds with. He applied a thin layer of mold release agent onto the masters, then he brushed on the RTV Silicone, for the first couple of layers, while following up by squeezing the tube, to fill in the remaining bulk. Be sure to put some keys into the mold, such that the two halves will only fit together one, precise way (minimizes mold lines). Also, be sure to apply a layer of mold release agent to the top surface of the bottom mold half, before you start applying the second half of the molding material!

The high-temperature RTV Silicone will allow you to cast using lead tire weights (free from automotive repair shops -- they have to pay to get rid of it!), or you can use more expensive Model Metal, available from Prince August, and other molding suppliers. Lead fishing weights can be purchased, and melted down for casting, but why pay for lead? The smelter can be purchased from fishing suppliers, too. Cheers!

Mingans Marauders Inactive Member14 Apr 2015 1:43 p.m. PST

Thank you everyone for the advice!

I should have noted the two part questions were for later on when we get used to just the general useage of working with molds and not for the bases.

We already picked up OOMOO 30 and I forget the resin, it was in a starter set together. I will have to look at the press cast stuff, seems like it would really useful for small parts!

You know we didnt really even think about dealing with lead, but after you mention it and reading else where that seems useful. Espically for figures or parts of them we want to do later on. Bases just seem overkill if done in metal, lol.

Brushing on the first few coats, never really thought of that but it makes perfect sense. Thank you!

Another question, would a figure with parts work best being molded with all of the arms and such on it, or better in pieces? I figure the pieces would work best for making it parts and doing different poses, but would doing it as a full figure just be easier in the end? Or does it depend more on how complex the sculpt is?

Thanks again!

shaun from s and s models Supporting Member of TMP15 Apr 2015 9:11 a.m. PST

unless you have a vacuum or a spin caster any figure with arms on will not mould very well, even the very thin resins do not cast very fine detail ok unless vacuumed.
good luck

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