Friday, March 26, 2004
Sculpting Epoxy Facts
Sculpting
The masters of wargames miniatures are sculped from various forms of epoxy -- green stuff, brown stuff, sculpty and so on. Here are a few handy facts about epoxy resins, silicones, and other two parts materials from Joel Haas in the Yahoo Sculpting Group. The handiest bit of knowledge: as a rule of thumb, for every 18 degrees Fahrenheit—10 degrees Celsius—you increase or decrease the temperature of the material, you will halve or double the curing time. That means, if an epoxy is rated to cure hard in two hours' time at 20 C or 70 F, then it will cure in one hour at 30 C or 88F; and, in a half hour at 40 C or 106 F; and in 15 minutes at 50 C or 124 F. The opposite is true as well—if you're working on a mini and somebody phones you, slip the mini in the freezer at about 30 F or a little under 0 C and the mini will stay workable when warmed for about 8 hours! I just kept a small toaster oven on my workbench set at "warm" (about 175F) and would slide one mini in to "cook" for a quarter hour or less while working on another one. They come out a bit rubbery when heated, but quickly regain their rigidity as they cool. Don't heat green stuff beyond 325 F, it melts at about 375 F! Why is "Green stuff" rubbery? I was told years ago it was because it was originally designed as plumbers' epoxy to patch copper pipes. Metal, of course, expands and contracts, so a completely rigid epoxy was not as good a sealant for water pipes as one that had a little bit of give. Two part chemical reactions –catalytic reactions --are "exothermic"—they give off heat as they take place. As we have just seen, heat makes the reaction set up even faster. That is why you don't see large solid balls of epoxy or polyesters, etc. cast. The heat from the reaction setting up is trapped in the middle and makes the whole mass set up at different rates and times, producing "crazing" and weak spots. With small scale casting, this is seldom a problem. If however, you wanted to get the epoxy to flow more into a mould with a lot crevices, etc, I suggest you cool the mould a bit so the epoxy will stay fluid longer and get to all the parts of the mould (don't try this with urethanes). If you have ever used car body repair putty (a filled polyester sold under the trade name BONDO in the USA) for making terrain, you have probably found it sets up in less than three minutes on a hot summer day and takes almost 15 minutes in the winter. RTV silicones, urethanes, etc. are all subject to the same heat sensitivity. A terrific standard and short—work on epoxies is INDUSTRIAL EPOXY PUTTYS by John A Wills. Though published in the mid 1980s, I had no problem finding copies offered for sale on the internet by typing in "INDUSTRIAL EPOXY PUTTYS" +Wills on Google. In addition to Polymeric's epoxies, I have used water cleaned, rigid epoxies by Aves http://www.aves.com and Magic Sculpt http://www.magicsculpt.com A good way to keep you dental tools for working minis clean—especially when working with green stuff—is to wear an old watch band with a Velcro patch on it. On the Velcro patch, just place a small wad of cotton soaked with mineral oil or baby oil and just keep wiping your tool over that. A lot more appealing than licking your tool all the time or using the oil off the end of your nose! Also, alcohol is an epoxy solvent, so try that if you can stand the smell. Joel Haas, sculptor
Entry Permalink and Comments | Email this entry | List All Posts By Category
Didn't find what you wanted? Try our exclusive Miniature Wargaming Search Engine.
Just wondering what sort of material is suitable for beginners? Since i would require longer work time so i can go back and make some changes to the sculpt… does that mean Sculpey is best choice for me?
Posted by (JavaScript must be enabled to view this email address) on 12/23 at 01:47 AM | #
From what I have read, green stuff is industry standard and Sculpey is only used by Rackham. This is because most minis companies have molds designed to be cast from green stuff. So if you want to make minis professionally, you need to get good with green stuff. But Sculpey is great to work for Rackham or to make your own minis, or if you will cast them yourself, as it’s not really much more expensive or troublesome to cast from Sculpey—it’s just not the standard and green stuff is.
I have read Sculpey is easier to use because it’s less pasty and obviously doesn’t dry until baked. It is however harder to make hard edges with when soft (though it can be filed after baking). If anyone has misgivings on the utility of Sculpey, click here:
http://carmensminiaturepainting.blogspot.com/
And see what Carmen has done shortly after discovering Sculpey.
Posted by (JavaScript must be enabled to view this email address) on 01/15 at 12:08 AM | #
Hi Jessica, I wasn’t reviewing anything, just passing on what I have read and donating a pretty valuable link for anyone who wants to see step-by-step how to sculpt 30mm with Sculpey.
As it turns out, I have started sculpting 30mm miniatures in several types of Sculpey and can comment on them:
Super Sculpey: (tan, cures orange). This is a popular medium for modellers and sculptors. First polymer clay I worked with. It was pretty easy to coat a wire armature with this and it holds detail pretty well. Howver for superfine detail or hard edges it sometimes leaves flash. I found it easy to use for making heads and faces as it’s not super sensitive (read below).
Super Sculpey Firm: (grey/grey, cures same color). This is the product they make for fine detail on miniatures. There is a 30mm miniature in their ad for this. I used this next. It is more sensitive than Super Sculpey which made it good for adding fine details like chain mail or etching on a scabbard. It’s also great for hard edges and cuts VERY clean, cleaner than Super Sculpey. For faces I found it too pliable; if I made a mistake, I had to start all over again each time. This was also harder to apply to a wire armature, so I used Super Sculpey for the body and this for the details, especially anything needing a hard edge.
PREMO Sculpey: (comes in colors) This is not meant to be painted like the Super Sculpeys, though you can if you want to. It is aimed at a more general audience. I have just started working with this one. Its properties are different from the above two. It holds its shape very well while working, maybe even better than Super Sculpey. Was very easy to apply to a wire armature.
Posted by (JavaScript must be enabled to view this email address) on 02/11 at 10:48 PM | #