I've started doing small workshops where I have attendees make a little styrofoam thingamabob, and then I add a sprue and cast it. Everyone absolutely loves what they get, but I'm trying to figure out how to improve the surface quality. I only have 2-3 hours between the sculpting and the pour, so there's no time for a dip coat. Another part of the challenge is that I'm using the same sand several times in a row, and it gets hot enough that it melts into the styrofoam a bit and adds more texture. Before I dive into experimentation, does anyone have tips for this situation? I'm thinking of trying out a few things next weekend: Packing a little bit of green sand around the pieces before they get packed in regular sand. This would prevent the hot sand from impinging on the styrofoam. But I'd lose that green sand since it would just get mixed in with my dry sand. Using foil tape to create decorative smooth spots. I'd have to be careful to leave plenty of room for outgassing into the sand though. Or maybe just spots of white glue would work in a similar way. Maybe there are some dip coats that would work though... I saw a formula which was water-based paint + chalk, which I think may dry quickly enough. An extremely thin coat of fast-set drywall compound? It retains moisture, but I'm wondering if it could be thin enough to not cause a problem. Then the practical thing: bringing more sand. But regardless, everyone who's made something has utterly loved getting it turned into metal, even at this level of quality. Thanks! Edit: I'm starting to wonder if there's a cheap color changing indicator additive to show when a dip coat is dry. I see a few out there, but they're not sold in small quantities.
Yes. And finer sand will producer better finish. -Might be your best bet but too fine may cause venting problems. Alcohol based coatings will dry much quicker but can be a fire hazard and ^$. You may be able to get a thin coat of drywall compound to dry within an hour with heat and forced air <110F. A hair dryer and a cardboard box for example but you will need to monitor it so it doesn't get too hot. A simple thermocouple should do for that. Just make sure you don't teach the next generation of casters that it's better to cast something poorly in 2hrs vs properly in a day. Best, Kelly
Any recommendations for one? I'm not sure where to start looking. They get a good profuse advance apology that things probably won't come out well, and that I'm skipping a few things like a dip coat.
Sorry, no. Water based always made more sense for me so I never gave alcohol based coatings much thought. The commerical coating suppliers offer them but I dont think they make much sense for a hobbyist because of cost, minimum buys, evaporation rates, and the commercial suppliers will never take you seriously nor sell to you. You could experiment with the dry drywall compound (mix your own stuff, it's very inexpensive and available at every big box retailer) as opposed to the premixed stuff. You may have to add some water to the alochol to get the drywall compound to mix and bond properly because I'm not sure pure Isopropyl alcohol alone will do that for gypsum/Plaster of Paris mixes. You can experiment with small amounts but are you willing to pay for a >gallon of Isopropyl Alcohol? Maybe Methanol but frankly, large amounts of combustible mix around novice casters doesn't sound like a good idea to me. I think you'd be far better off making a drying box and sticking with safe and simple water based compound. Best, Kelly
Have you tried using a kitchen sieve held chin high and let the sand cascade down? I've used that method to cool the sand before storing it in a plastic bucket.
I've been getting some good results using graphite mixed with shellac dissolved in ethanol for various release coatings and thought it might be good for a mould coating too considering dry graphite brushed on sand works well. It dries in minutes and has decent mechanical strength but needs constant stirring as it settles fast. It won't have much mechanical strength so it'd need good tight sand packing. Maybe sprinkling sand on it while still wet would built up a fast drying shell with some support.
A hairdryer and a cardboard dryer box would be the way to go. Hang the dipped pieces in a cardboard box, apply hairdryer as needed. That would leave you free to do whatever else you want. Fredo
I have a dehumidifier that drys the coating a lot quicker when I hang them in the dry air coming out of it. A box would likely help.
I’m thinking of a setup with a small fan circulating air through desiccant, plus maybe something to increase the temp.
