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Hi Melody! I have a question about your casting process: how do you create such wonderfully bubble-free casts? I work in my school’s fossil preparation lab where we mold and cast all sorts of things in all sorts of materials. We often use plaster and gypsum stone, but have a lot of trouble with keeping bubbles from appearing on the surface of our casts, and occupying the ‘tips’ of our casts. The common method for reducing the bubbles is tapping the molds once they’re poured, but this never gets rid of the problem. Do you guys have some sort of vaccuming process which eliminates air from the slurry before or after it’s poured?
Sorry for the long question, thanks a lot!
Forever seeking: Blackwatch the raffle Old Warrior, Jennifer Miller's pieces, and GB Baby unis!
Zelda wrote:Hi Melody! I have a question about your casting process: how do you create such wonderfully bubble-free casts? I work in my school’s fossil preparation lab where we mold and cast all sorts of things in all sorts of materials. We often use plaster and gypsum stone, but have a lot of trouble with keeping bubbles from appearing on the surface of our casts, and occupying the ‘tips’ of our casts. The common method for reducing the bubbles is tapping the molds once they’re poured, but this never gets rid of the problem. Do you guys have some sort of vaccuming process which eliminates air from the slurry before or after it’s poured?
Sorry for the long question, thanks a lot! Sorry this took so long to answer, part of my New Year’s resoultion is to spend less time onlne,and more time drawing. Silly, really.
I can’t answer specific questions about our casting process because we kinda worked it out over many years and it is sort-of our secret. However I will say that we don’t have a magic method and we get lots of bubbles too! (A long paintbrush can be used get out the deep bubbles) Sometimes it has to do with the batch of plaster, or the weather… or the person doing the casting! Just the hand that pours it seems to make a difference in the amount of bubbles. It is totally Voodoo.In school when we were learning how to pour slip into molds we had a table type thing that we set them on. It vibrated them ever so slightly, to encourage the bubbles to the top.
my tiny experience, though I only made it one time, is to have a big mold (with lots of space in the fill in art) and only fill in part of the liquid(1/4), grab the mold and shake it, especially into the directions of difficult parts (like with a sitting wolf its the snout), then secure the mold and not slightly but violently shake it for one full minute. Works easyly by securing (you dont want jumping molds!) the whole thing on a small table and then knocking sidewise of it with your fist like you’r playing a… galleons drum.
I suggest you try with wall plaster first before you use the special plaster 😉
and as I said in another thread (didnt try it yet) vakuum would work too. Hope this helps 🙂I have no experience with molds or sculpting, but I wonder if it would work to put your mold in an ultrasonic cleaner? The basic principle behind those is to use ultrasonics to agitate the solution by causing bubbles to form and collapse.
So I wonder if ultrasonics would also be able to cause air bubbles which are sticking to the sides of the mold to come loose and float to the top? Its basically the same idea as tapping or vibrating the molds which people mentioned in the previous posts, except that you’re using ultrasonics to do it, and its being done on a molecular level.
Of course, your mold would have to be completely waterproof since you need to put the mold in the ultrasonic cleaner solution (the solution can just be water in this case). And there are some other factors to consider — the properties of the mold material and slurry would affect how well the ultrasonics would work, and the ultrasonics could possibly have a detrimental effect on the slurry (it might be OK though…ultrasonic cleaners are routinely used for electronics). I guess you’d have to actually try it to find out whether its feasible.
Thanks to Melody and others for your suggestions! The vibrating method is something we do by hand, tapping the molds, with variable success. We run a pretty low-tech operation so the cleaner and the vibrating table aren’t much of an option. Thanks to seeing Melody’s gallery pictures, as well as the work of others with molding and casting expertise, I can say it’s a much better option to have flat-sided mother molds that can be banded or screwed together.
And BTW Melody, there’s nothing negative at all with drawing more! Best of luck!
Forever seeking: Blackwatch the raffle Old Warrior, Jennifer Miller's pieces, and GB Baby unis!
Zelda wrote:Thanks to Melody and others for your suggestions! The vibrating method is something we do by hand, tapping the molds, with variable success. We run a pretty low-tech operation so the cleaner and the vibrating table aren’t much of an option. Thanks to seeing Melody’s gallery pictures, as well as the work of others with molding and casting expertise, I can say it’s a much better option to have flat-sided mother molds that can be banded or screwed together.
And BTW Melody, there’s nothing negative at all with drawing more! Best of luck!
We patch the previous batch of casting’s bubbles with the plaster from the next batch. The trick is to patch them quick, before they dry out.
I’m drawing like crazy , thanks!
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