Rainy day project...

[HarveyH48]

Been raining pretty steady all day, so took care of a few chores. Was going to mess around with a penny sorter project, but got a little side tracked, after finding that the slot machine spare hopper I was looking for, was in parts an pieces, then remembered I need something off it, to get the working one to use quarters. Still have another hopper, but it's in another machine I never messed with much after the initial sparks from just plugging it in...

Anyway, found a plaster casting of a Labrador dog, had planned on someday making a mold to cast in pewter. Read about using silcone caulk, thinned with paint thinner. I just happened to have an unused tube, from fixing my bathroom sink a couple of months ago, half a gallon, of some really old paint thinner. The caulk was the cheapest silicone Walmart had, wasn't sure I was going to need it, but figured it best to have ready, just in case.

I found a cardboard box, right size, lined it with tinfoil, placed the plaster cast in the middle, then started mixing. Didn't measure anything, was more interested in getting a syrupy consistency. Did about half the tube of silicone, poured it in, little clumpy though. Just barely covered the piece, so mixed up the rest. Stirred it up a lot better this time, didn't notice the chunks, and brought it up to a good thickness.

Have no idea how this is going to turn out, just an experiment I've been wanting to try for years. Thinking it could take days for this thing to setup and cure. Will probably wait a week or more, before attempting to pour hot metal into it. There will be air bubbles in it, may shrink some too. I'm not positive that it will hold up to the heat at all. Really don't expect a perfect mold, or a perfect cast, pretty sloppy work. But it does work out, it's pretty cheap and easy way to make molds, and could be a way to use some of the lead fishing weights, tire weights, and so forth.

[Gauntlet]

Would give me good reason to eat more Deep-Dish Pizzas

Interested in seeing what it looks like when you peel it off.

[carcur]

interesting
i remember making sand molds in metals class in Jr high school

[HarveyH48]

I'll post pictures of it. Little over 12 hours later, it feels like Jello, but not wet or tacky. Will have to see what it's like after work. Kind of look like it'll be several days at this rate. I don't think I need to wait until it's completely solid to remove the plaster model, but will have to wait until using it for metal. I do want to get out of the box though, more exposed it is, quicker it will cure. Think the tube mentioned something about 24 hours, but that was for a thin application. Probably shouldn't have used the whole tube, but I knew that any of it left, would probably dry out and get thrown away before it got used anyway...

Thought about green sand once, but it seemed like a lot of work, for a single cast. It's good for somethings, but I want a mold that can be used a several times. There are silicone products, specifically made for this, but kind of expensive, come in two parts, which need to be mixed semi-accurately. Never got around to giving them a try, and will probably find out why more people don't do this on the cheap. The thinning agent was the only thing holding me back, and after reading about paint thinner, it's been stuck in my mind.

What's cool though, if this works, is you can model with clay, or just about anything. Lead and tin will melt on the stove top, old cast iron pot. So pretty much anyone can get into making stuff at home, for very little money. The metal can be had for basically free. I used to get lead tire weights free for the asking, at the tire place down the street.

[Gauntlet]

I wouldn't smelt lead inside your house because of the fumes. Use a turkey cooker outside. You can make a pot from a section of heavy wall pipe by welding-in a bottom, a section of smaller pipe for a spout, and tabs for a wire handle. You also should wear a (good) respirator and heavy gloves while smelting.

[HarveyH48]

Originally Posted by Gauntlet

I wouldn't smelt lead inside your house because of the fumes. Use a turkey cooker outside. You can make a pot from a section of heavy wall pipe by welding-in a bottom, a section of smaller pipe for a spout, and tabs for a wire handle. You also should wear a (good) respirator and heavy gloves while smelting.

I've been casting metals for a while, just not making many molds. I've got a 10 pound Lee melting pot, and a pretty large assortment of store bought molds for figurines. I've got some pretty old metal molds, but they don't work well most of the time.

Use leather welding gloves. Usually have a window open for ventilation, and to move out some of the heat. Usually stand back far enough not to breathing heavy fumes anyway. The tire weights, and anything else I pick up, usually gets melted down outside first(propane cooker, cast iron pot), and cast into ingots (aluminum muffin pan), because there are a lot of fumes from the oil and road grime, also a good deal of slag. Use a large speaker magnet to remove the iron tabs, just easier than trying to fish them out.

Never used a respirator, wash my hands often, and well after done handling the lead. Most lead poisoning comes from ingesting.

Think this mold is going to take a while. Was poking at it, still a lot like jello, might still be kind of liquid under a thick, tough skin. Still very spongy and flexible, expected it to be sort of rigid. Don't think it's set up enough to pull out of the box or remove the foil.

[HarveyH48]

Well, three days later, and still not feeling solid. I pulled it out of the box, but left the foil on. The underside felt soft, maybe still fluid. The foil is stuck pretty good, so likely have to cut it off later.

Foil was a bad idea, will just use cardboard, or maybe just printer paper next time. Needs to breath. I'm sure this one will get solid, eventually, but looks like weeks at the rate it's going. Also, probably thinned the caulk more than I needed to, not a lot of fine detail. Also need to seal the model to the base, got some large air pockets, but don't think they will hurt the cast, the mold might not last as long as it could.

Going to try again this weekend, with what I've learned. German Shepard this time. Will try to keep the thickness of the mold down some too, maybe a quarter inch above the highest point. Hopefully, this will get me a working mold in a week or two.

[Gauntlet]

Harvey, try cutting some slits in the foil with a razor knife.

[Hotrod Tom]

I think your using the wrong kind of silicone. Here's a video of how to do it.

http://www.youtube.com/watch?v=M400d...e_gdata_player

[HarveyH48]

Thanks. Only watch enough of the video, to see what product it was. I'm on dial-up, so that whole 5 minutes would take a while. The two part silicone is sort of expensive, was hoping to try and do it cheap. I realize there is plenty of room for failure here, but a success at a fraction of the cost would be awesome. I've read the process a few times, on the site I bought most of my molds from, the also sell several products for making your own molds. http://miniaturemolds.com/

Just happened to read something about paint thinner and silicone caulk, and had a spare tube, some very old paint thinner on hand, and a rainy day. Only out about $3.00 if it's a complete failure.

It's definitely getting solid, and starting to feel more like a slab. Going to give it another day, see what I've got to support it, keep it relatively flat, and provide good circulation. Then, I flip it over, and remove some of the foil, maybe all that's currently the bottom. Still feels very soft and fluid. Going to put a fan blowing on it, in a few minutes, might help speed it some.

[HarveyH48]

Got it flipped over, and peeled back the foil. Yep, it was wet gel. Don't think the model will sink, but going to have to clean up the edges after it sets.

[HarveyH48]

Well, something went horribly wrong with the first attempt, it still wet and tacky. So, Sunday afternoon, I got around to doing the German Shepard. Made the form from card stock, one inch sides, about 7.5 inches square. Mixed the whole tube again, larger form. Unfortunately, the jar I was mixing in, wasn't big enough to add enough to make the silicone fluid. More like toothpaste or cake frosting. Still worked out okay, just spread it over the model best I could. Set up pretty good the first day. This morning, the card stock got a little damp, so removed all I could. Just got home from work, and removed the plaster model.

Looks pretty good, going to pour the metal this weekend. Figure two more days, and it will be cured as much as it'll get. Don't think it's going to catch fire or anything. It is kind of thin though, and the bottom isn't even or flat. Hoping I've still got some sand or gravel to use as support. Could just use dirt, mostly sand.

Figure if I can get one good cast, it's worth the cost of the mold materials. Half dozen or so, before it fails, and it's awesome. Really hoping that the difference between cheap Walmart brand silicone caulk, and the two part silicone rubber, is just how many casts it will last. That it's expensive, because the mold will last a long time.