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Dave Parvin
Joined:
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16-Mar-2005
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Started On : 07-Jun-2009 at 01:08:10 PM, #Views : 6033
Topic Subject : More on Mixing Alginate |
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I am constantly searching for better ways of doing things. In fact, on my studio wall it says, "There is almost always a better way." Or as avery good friend, Mike Sisbarro, says, "If I have been doing something the same way for a long time, I'm probably doing it wrong because someone has almost certainly come up with a better way." I really love to hear different ways of doing things.
But back to mixing alginate. I find that high speed "Jiffy Mixers" and their lower priced generic paint mixers do just fine. About 2 1/2 inches (10 centimeters) wide for batches of alginate requiring up to about 6 pounds (around 3 liters) of water. I get zero surface bubbles with applied alginate skin molds and almost zero with block, pour, or plunge molds. Nevertheless, I am very curious about the 'rotary vibrator" mixer. Bruce, could you provide a description and a source. Also, how long would it take to mix, say, 4 to 6 pounds of water with the proper amount of alginate. I have a "Whip Mixer" which is a vacuum mixer made for dental labs which does a wonderful job but can only small batches.
I respect John, a true giant among life casters, immensely and take whatever he says as gospel. But adding water to alginate and relying on experience to determine the correct consistency just SEEMS more difficult to do and harder to teach than determining the correct ratio, measuring the water and alginate by weight, adding the alginate to the water and mixing. It just SEEMS that the latter would be simpler, faster, and more consistent. But, I agree with John, "To each his own."
As for casting hand by plunging or by application. I use both methods depending on the project. Last July, 20 assistants and myself cast 768 hands in 5 1/2 hours by plunging. That works out to a hand every 30.5 seconds. True, we used more alginate than we would have used by applying alginate to the hands, but we could not have done so many with so few. (Sort of like the Battle of Briton; no disrespect meant John and Ann.)
Just as I as about to post this, I got CJ's reply. My experience with students has been just the opposite. Student have wanted know what proportions to use and rather than just add until it feels right. "Feels right "doesn't mean much to someone who is a newby. As for myself, I always measure alginate and water for speed and consistency. As I wrote previously, I usually mix up to six pounds of water plus the alginate in one minute and the mixture is correct. For a skin mold, the alginate will stay in place on the model about 3/16 of an inch thick without dripping or running and with excellent detail and minimal flaws. When I have mixed alginate to feel, it has taken me longer to get it right. Perhaps with practice, I could shorten the time. Since even slow set alginates have a relatively short pot life, I would much prefer to use the time in applying it carefully to the model than mixing which is an absolute no brainer if one knows the correct proportions. I do not measure plaster whose proportions are much more forgiving than alginate's. I use the electric drills and mixers for the plasters as well because it is so quick and easy. Also, I do not use plaster, hydocal, etc. as final casting materials but only in intermediate steps. If I'm not casting in bronze or raku firing, I use resins or Forton MG which I do measure. However, I provide the correct water gypsum products proportions to my students and recommend that they follow them until they have enough experience to know what is acceptable by feel. But whatever works for you is the right way to do it; what is important is that we all keep doing it and sharing our ideas. Dave
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