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Hello, workshop attendees!
1) I'll be explaining how to use oyumaru clay, polymer clay, greenstuff, and two-part room temperature vulcanizing (RTV) rubber to make molds.
2) Everyone will get some hands-on experience using RTV to make a mold.
3) As the event description says, "Suitable items for copying are provided, but feel free to bring your own creations if you want to experiment." If you bring your own item, please make sure it's no larger than about 1 cubic inch; there's a limited amount of RTV material to make molds with, and I want to make sure everyone gets a reasonable amount to use.
4) If you bring in your own item to copy, it should have no undercuts or very minimal undercuts. What's an undercut? I made some pictures to help explain.
• Say you have a weird little statue you want to make a mold of.
• We'll place it on the table, build a square frame around it out of LEGO bricks (red), and fill the space around the statue with RTV moldmaker liquid (blue). The liquid turns solid (but flexible) after about 4 hours, and then we can remove the original statue through the hole left where the statue touches the table.
• To use the mold, you turn it upside down and pour the casting material (usually resin or dental plaster) into the hole in the bottom. Original item has places where it is narrower next to wider areas (yellow arrows), it can be hard to extract the finished cast without tearing the mold (because you have to pull the wider, lower part of the cast item through the narrow part of the mold). It also means that the casting material may have a problem flowing into all recesses of the mold.
That's why this method works best on mostly-flattish items such as shields, doors, floor tiles, sarcophagus lids, Han Solo in carbonite, and so on. It can produce some good results if the undercuts are minimal or you're willing to accept some errors on the cast part (for example, if you're casting a statue, the errors in the cast can be explained as damage to the statue. For example, I sculpted this monster and made two casts of it and they still turned out pretty good despite some undercuts.
TLDR: If you want to bring your own item to copy, don't bring a 28mm miniature with the expectation that you'll be able to make a perfect copy of it. Maybe a compact monster, or a skull, or something like that.
Hey, workshoppers! If you too your mold with you, here are some tips for extracting your original from the mold (especially as we didn't use mold release):
1) Peel the mold away from the cardboard.
2) Remove the Lego bricks before you do anything else.
3) Be slow, be gentle. Turn the mold upside-down and look at where the bottom of the master is. The blue stuff is flexible, so you can bend it away from that point, causing it to slowly peel off of the master (unlike ripping off an adhesive bandage in one quick pull, you want to do this slowly so as to not damage the mold).
4) Work one side, then another, until all sides are pulled free of the mold, at which point you might be able to bend the mold "open" and pull the master straight out.
5) If the mold tears a little bit, that's okay... it'll close up again when you allow the mold to relax, and that'll mostly seal it when you want to use it for casts.
And here's a link to my Facebook album showing some of the things we were talking about in the workshop.
Here's a pic of Theresa's goblin head mold.
Here's a pic of Sarah's bird coin mold.
Here are the product links I handed out, just in case you lose the paper or didn't attend the workshop:
Apoxie Sculpt (Hard Epoxy Clay)
Excalibur (Dental Plaster)
(or ask your local dentist/orthodontist)
Hydrocal (Dental Plaster)
(or ask your local dentist/orthodontist)
Kneadatite (Greenstuff)[/url]
(buy the tubes, not the tap with the cured part in the middle)
One-To-One Rapid Mold Rubber (Blue Stuff)
Sculpey (Sculpting Stuff)
Just about anywhere, including department stores, art stores, craft stores, and the internet.
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Thank you again for the workshop! It was very fun. Perhaps next year it would be helpful to include a more detailed handout? I wanted to share the experience with people who couldn't make it, but the details got fuzzy. I am still unsure of say...when to use different materials, or what is best for more complex pieces. Something like that would make it perfect!
Yep, sounds good (this was my first time doing this workshop, and everything gets hectic before the con and I ran out of time to prepare a more detailed handout).
Try it with plaster of paris... same principle, but much cheaper. :)
BTW, everyone who left their molds with me so they could cure and I could mail them back to you... your addresses are in the box of materials, which is still on a palette from PaizoCon, as the warehouse team is busy shipping a bunch of stuff this week. I'll send 'em out once I get the box. :)