Casting With Alginate and Resin
- Thread starter Joe Campbell
- Start date
Wow, this thread has become a fountain of useful information I never knew before.
Can you paint hot glue molded pieces?
Can you paint hot glue molded pieces?
Weapioneer
Active Member
To an extent. Thick paint will surely crack and flake off, but thin coats of acrylic should stay if you don't bend it too often. Maybe latex paint might work, but i don't have any. It is also a good idea to try to colour the hot glue itself.
Never used alginate, but it sounds like it might work for a throw away mold I'm needing.
Working on a grail tablet and almost have the surface done, still need to sculpt the edges. My master is a mixture of materials so it doesn't sand evenly when I go to true up the surface and make some repairs. Plan was to mold just the lettering/cross, cast in something easy to work on like PoP and add the sides to it.
Questions:
1) How well does it release from the master?
2) Does PoP cast well in it?
3) How far would 3lbs go? (Need to do around 20"x20" and 1/2" thick)
If it goes right, I would pull one PoP cast, trash the mold, and use the PoP cast later to make a silicone mold once I true the surface and add the edges.
Working on a grail tablet and almost have the surface done, still need to sculpt the edges. My master is a mixture of materials so it doesn't sand evenly when I go to true up the surface and make some repairs. Plan was to mold just the lettering/cross, cast in something easy to work on like PoP and add the sides to it.
Questions:
1) How well does it release from the master?
2) Does PoP cast well in it?
3) How far would 3lbs go? (Need to do around 20"x20" and 1/2" thick)
If it goes right, I would pull one PoP cast, trash the mold, and use the PoP cast later to make a silicone mold once I true the surface and add the edges.
Weapioneer
Active Member
Alginate releases from plastecine really easily, the soft plastecine isn't damaged at all. I don't use any release agents, and whether it would release depends on the material of the master. Plaster of paris should cast fine in alginate, just make sure it is dry before removing it from the master and casting. I made 2 casts so far, for ezio's pauldron buckle and the assassin's insignia on his waist. I still have more than half a pound of plasticine left. 3 pounds of plastecine should be enough, but if you are going to use all of that at once, you will have trouble. Alginate is a fine dry powder, and once you add water it begins to clump up and starts to set. It MUST be thoroughly stirred before applying, and it is pretty thick. Imagine trying to use bondo, except it is slightly thicker.
It is fine for smaller molds but larger molds will give you hell trying to mix it and slather it onto the master in less than 2-3 min. It does depend on the variety of alginate though, I just bought mine from a local dentist. What ever you find maybe easier to work with than mine. Also, it is cured by slight heat, not exothermic though, so cold water should extend working time. for something that large, you might want to either mix and slather in batches or use a different molding material. Consider using hot glue as a mold making material, i hear it works well.
Good luck!
Don't use alginate in batches. Once cured, it doesn't actually bond to itself. You'll simply be peeling layers of alginate away from each other. Use a hand drill and some kind of mixing bit to mix up large batches, otherwise the alginate will end up somewhat lumpy, and this WILL translate into the surface of your mould.
Use the silicone.
"there is never enough time to do it right, but there is always enough time to do it over"
Frank
"there is never enough time to do it right, but there is always enough time to do it over"
Frank
This is very true. Although they do make a bonding agent you can spray on a batch that has set so a new batch will bond to it, it is really for emergencies (the seam will show). Besides, once you start getting into that you might as well use silicone, like Brundelfly said.
This is good advice, even for smaller batches. You might want to practice with small batches first to get the timing down, because when you're learning, it seems to get to just the right consistency 5 seconds before it sets.
And use cold, cold water to retard the setting time. Hot water will doom you.
- JD
Given the consistancy then, I don't believe it would work for me. I assumed it to be about like pourable silicone.
I don't want to lose any details as my method for lettering was pretty intensive and very detailed.
I'll just do a thin coat of silicone as a waste mold. Will back it with a hard and very flat surface.
Weapioneer
Active Member
Yes, That would work much better than alginate in this case. Alginate is still useful for those who can't get silicone rubber or other molding agents, but while it takes detailing like fine engraving well, it also tends to get bubbles, which necessitates a lot of clean up on the casting.
Try rinsing alginate with thinner that's compatible with resin. I've had good results with polyester resins.
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