Weird question, but some of you guys might have tried it.
Some time ago I was watching one of those "how do they do it?"-type shows on Discovery and the segment was about jelly beans, and how they are made by pouring hot candy on dimples made on a tray filled with cornstarch. That got me thinking how similar this method is to sand-mold casting of metals, and then on to is this kind of process could be adapted to cast small resin parts.
The mold would have to be shallow, one-sided, with no overhangs; the part would have to be quite small and its texture would end 'pebbly' in scale (maybe 'sandy'), as if the original had been cast using sand molds.
If the resin is thick enough, and it has no water to react with the starch, and sometimes starch is used as mold-release, I know it doesn't react badly with the resin.
Now the 64-thousand-dollar question: Has anybody attempted something like it? If so, did it work? Did it kinda work?
Corn starch as a mold-making material?
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Chacal
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Corn starch as a mold-making material?
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We tried something like that with Moonsand, a sticky sand toy.
Made a mess.
I'd suspect the same thing would happen with cornstarch. The power will wick away fluid from the resin. You'd have to go with both a thick resin and a fast setting one to avoid the powder making a mess of things.
In making gel candies the material sets very quickly and doesn't have a chance to wick out into the power.
Made a mess.
I'd suspect the same thing would happen with cornstarch. The power will wick away fluid from the resin. You'd have to go with both a thick resin and a fast setting one to avoid the powder making a mess of things.
In making gel candies the material sets very quickly and doesn't have a chance to wick out into the power.
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About the only way to use cornstarch for casting is how they used it
As a coating on the mold to prevent stickage - just like you'd use the spray Mold Releases
Talcum powder also works well for this method
The problem with using powders as the actual molds is that there IS low viscosity liquid in the resin - this is especially true with the ultra-low viscosity resins like SC-300 or 320 series - water thin
The resin will seep out though the powder - unlike metals (a friend is a blacksmith who also does bronze sand-casting) which are relatively high viscosity compared to resins
Stick with the rubber or plaster-backed rubber molds for resin - you'll be happier in the long run
As a coating on the mold to prevent stickage - just like you'd use the spray Mold Releases
Talcum powder also works well for this method
The problem with using powders as the actual molds is that there IS low viscosity liquid in the resin - this is especially true with the ultra-low viscosity resins like SC-300 or 320 series - water thin
The resin will seep out though the powder - unlike metals (a friend is a blacksmith who also does bronze sand-casting) which are relatively high viscosity compared to resins
Stick with the rubber or plaster-backed rubber molds for resin - you'll be happier in the long run
Hey, now that's cool.eeun wrote:Used to make the mold, rather than the cast, corn starch can be useful for small stuff or quick one-offs:
Link (sorry, it's an instructable. Can't stand their formatting)
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This model was supposedly stereolithographed using cornstarch and gypsum (plaster?). Weird, but it looks ok.
http://www.starshipmodeler.us/gallery14 ... rsbase.htm
http://www.starshipmodeler.us/gallery14 ... rsbase.htm