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Old 03-11-2014, 05:44 PM   #11
jollyskeleton
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Thanks for the kind offer of continued advice! I will go check out my local store to see if they sell suitable silicones. I reckon like you say, the first couple times will be figuring out how to handle the stuff
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Old 04-01-2014, 11:59 AM   #12
Pucho
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Quick question. Has anyone tried using alginate for waste molds? They are very brittle and not perfect, but it seems like a perfect fit for this type of application (considering its price)...
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Old 04-01-2014, 05:57 PM   #13
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i have thought of this as well. and i have actually been considering this method. but have yet to try it. and with it being brittle might not be a good idea. unless you can figure out a way to do a two piece mold with the alginate.
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Old 04-02-2014, 02:59 AM   #14
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I wouldn't recommend alginates too much. Am a dental student and we use it for impressions. It's not particularly dimensionally stable, and warps over time. It can also tear in some rigid sections. It also sets quite quickly (in minutes. Although there are fast set and slightly slower set and depends on powder:liquid ration), easily entrapping air bubbles and such, requires you to work extremely efficiently and carefully to get it where you want to.

That being said, I'm thinking that if you loaded a silicone tray (one of those flexible baking type ones) with alginate and submerge half the sculpt in carefully, you'll be able to retrieve the mold and at the same time remove the sculpt from the impression. Repeat for the second half. Not tried for moulding sculpts myself, but just speculating here


Alginates need to be kept moist and covered, and casts should be poured up as quickly as possible, or the impression warps and becomes inaccurate
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Old 04-02-2014, 07:22 AM   #15
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Splendid! Thanks for the ace in the hole on the molding!
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Old 04-02-2014, 01:07 PM   #16
DynamicMenace
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Quote:
Originally Posted by jollyskeleton View Post
I wouldn't recommend alginates too much. Am a dental student and we use it for impressions. It's not particularly dimensionally stable, and warps over time. It can also tear in some rigid sections. It also sets quite quickly (in minutes. Although there are fast set and slightly slower set and depends on powder:liquid ration), easily entrapping air bubbles and such, requires you to work extremely efficiently and carefully to get it where you want to.

That being said, I'm thinking that if you loaded a silicone tray (one of those flexible baking type ones) with alginate and submerge half the sculpt in carefully, you'll be able to retrieve the mold and at the same time remove the sculpt from the impression. Repeat for the second half. Not tried for moulding sculpts myself, but just speculating here


Alginates need to be kept moist and covered, and casts should be poured up as quickly as possible, or the impression warps and becomes inaccurate
well the molds would only be used one time. thats why they are called waste molds.

you have a pretty good idea for the two piece molds for the alginate. but what you have to take into consideration is that the second half needs to be an exact match to the surface of the first alginate mold. and the only way to accomplish this is to pour the alginate directly onto the first mold while the model is still in the mold. then you have to worry about how to make keys in the mold so that it wont move or separate while casting. but thats pretty easy for you can use acorn nuts for that on the first part of the mold and then remove them. and thats only if they dont sick too far into the alginate..lol. but then there is the question, does alginate stick to cured alginate if pouring directly to the first aliginate mold? if so can you use mold release so that they dont stick together like you can with silicone?
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Old 04-02-2014, 05:02 PM   #17
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Nice discussion here I don't have any experience dealing with alginates but from what I read online, they are quite troublesome to work with.

With the silicone at least, you actually have enough time to pop the entire thing into a pressure chamber and get rid of all your bubbles before it sets. Just make sure your piece isn't hollow...
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Old 04-02-2014, 06:30 PM   #18
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you actually need to vacuum the silicone prior to putting it into the PP to get rid of the bubbles. but you dont have to with the resin. you can just put that right into the PP and that should get rid of all the bubbles. with the proper ventilation of course.
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Old 04-03-2014, 08:20 AM   #19
jollyskeleton
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actually, not too sure if fresh alginate sticks to old ones. Never had a cause to do so. I doubt it sticks well, but in the worst case, a bit of vaseline should do the trick I suppose.
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Old 04-04-2014, 03:30 PM   #20
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Quote:
Originally Posted by DynamicMenace View Post
you actually need to vacuum the silicone prior to putting it into the PP to get rid of the bubbles. but you dont have to with the resin. you can just put that right into the PP and that should get rid of all the bubbles. with the proper ventilation of course.
Agreed, I do both with the expensive silicone, vacuum and then pp.

I should've been more detailed in my explanation earlier, I meant for my waste mold method, putting the entire mold into the pp and putting it to 50 PSI will press the thick silicone into all the nooks and crannies

I guess bubbles wasn't the best term to use lol, air pockets would make more sense.
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