chachybaby Posted September 15, 2011 Report Share Posted September 15, 2011 Hey guys, this is probably been asked tons of times, sorry if a repost, I was wondering, I'm in the process of making a two piece POP mold. The first half is done, it has the baits still in. What are my next steps? Also, for future molds, how do I measure how much POP to add per mold? Its two parts POP to one part water. How can I measure the container to see how much POP I need to add? Thx guys, C Quote Link to comment Share on other sites More sharing options...
gone2long Posted September 15, 2011 Report Share Posted September 15, 2011 I've seen guys remove the baits from side 1 and sand until the under cut was gone then re-insert the baits to pour side 2, as for determining amount just fill the mold with water both for side 1 then side 2 before hand then just mark level for each and pour off into a measuring cup. Quote Link to comment Share on other sites More sharing options...
chachybaby Posted September 15, 2011 Author Report Share Posted September 15, 2011 which part is the undercut? Quote Link to comment Share on other sites More sharing options...
FishBones Posted September 15, 2011 Report Share Posted September 15, 2011 The undercut is the part of the mold that makes a "lip" around the flat side (top usually) of the bait. It's usually caused as the mold material creeps underneath the part a little bit even though you glued it down really well. With hard molds after hardening you sand down the face after removing the masters until you have a clean edge to the mold cavities. With soft, silicone molds I just trim the edges with an exacto knife. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted September 15, 2011 Report Share Posted September 15, 2011 (edited) Because I am not making PoP molds regularly, I usually end up doing a Google search to find the mix ratio numbers. But I think it was less PoP than you are using. A thinner mix than 2:1 will help with the bubble removal. Experimenting with mixes is allowed. I measure the volume of the mold, by filling with water and pouring into a jug. This is my water content and I work out the volume of PoP from this. Yes, I end up with more mix than I need, but PoP is cheap. It is always better to mix too much than not enough. This method also tests my mold box for leaks. Nothing worse than PoP mix leaking out after all that preparation. Dave Edited September 15, 2011 by Vodkaman Quote Link to comment Share on other sites More sharing options...
chachybaby Posted September 15, 2011 Author Report Share Posted September 15, 2011 guys sorry to be such a newb, but I'm not seeing this undercut... walk me through it. The plaster has set in the box I made for the mold, the baits are set in half way in the middle with the plaster set around it. The box is half full, the other half will be poured for the second half of the mold. So I remove the baits from the mold.. what am I looking to sand down??? And what can I use to sand it with?? Won't a fine grit sand paper leave a grey residue over it?? My understanding is sand it down to produce a completely smooth surface, so the second half will be the same...? Thanks, C Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted September 16, 2011 Report Share Posted September 16, 2011 If your baits are already set half way, then the sanding operation is not necessary. Have you cut some keying indents, to locate both halves of the mold, so that the cavities will line up when pouring. Dave Quote Link to comment Share on other sites More sharing options...
chachybaby Posted September 16, 2011 Author Report Share Posted September 16, 2011 ohh ok, yes, that part has been done, inserted a couple stainless steal screws that pop out about a 1/4" in opposite corners. Quote Link to comment Share on other sites More sharing options...
gone2long Posted September 16, 2011 Report Share Posted September 16, 2011 OK. this is not a PoP mold but you will get the idea of what an undercut is from this video, and by the way outside of the New York accent this is a good technique with fiberglass resin. Quote Link to comment Share on other sites More sharing options...
chachybaby Posted September 16, 2011 Author Report Share Posted September 16, 2011 should I still sand it flat around the baits? if so what can I use? Quote Link to comment Share on other sites More sharing options...
gone2long Posted September 16, 2011 Report Share Posted September 16, 2011 I would it won't hurt, it really depends on how well your side one turns out, but I'll tell you it's rare to get a perfect side as plaster seams to find it's way around the best secured bait. Quote Link to comment Share on other sites More sharing options...
chachybaby Posted September 20, 2011 Author Report Share Posted September 20, 2011 guys, any ideas on what to use to sand PoP?? Quote Link to comment Share on other sites More sharing options...
gone2long Posted September 20, 2011 Report Share Posted September 20, 2011 guys, any ideas on what to use to sand PoP?? Just use a flat block of wood and some sand paper the grit number will all depend on the condition of your first side, remember your going to seal side 1 before pouring side 2 on top so it doesn't have to be perfect. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted September 21, 2011 Report Share Posted September 21, 2011 Sanding PoP is a real pain. If the PoP is not completely dry, it will immediately clog up the paper. I dry my PoP first, glue a sheet of coarse emery to a board and sand with figure 8 motion. When the paper is clogged, I blast it with high pressure air from the compressor. This works well for me. Dave Quote Link to comment Share on other sites More sharing options...
chachybaby Posted September 23, 2011 Author Report Share Posted September 23, 2011 hey guys, just finished pouring the second half of the two part mold. I waited a night and then today I seperated the two pieces. Few questions: Can I go ahead and seal the mold at this point after cleaning up the rough edges etc?? How do I make the pouring chambers at the top? Can I fit the two together and drill a hole through?? After sealing a few coats with 50/50 water and elmers glue all, how long does it take for it to dry? Thanks, C Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted September 23, 2011 Report Share Posted September 23, 2011 No. You have to completely dry both halves of the mold. Weigh them and keep drying until the stop losing weight. Dave Quote Link to comment Share on other sites More sharing options...
chachybaby Posted September 23, 2011 Author Report Share Posted September 23, 2011 hey Dave, sorry forgot to mention i started drying them as well last night. Baked them in the oven for a little over an hour at 325 with the door slightly open. They are about an inch and quarter thick. I baked till I could not see as much condensation rising from them. I wrapped them in newspaper for a half hour, and now they are on the bench drying some more. Hope i'm on the right path Quote Link to comment Share on other sites More sharing options...
SHK Posted September 23, 2011 Report Share Posted September 23, 2011 be careful, i dont think you want to exceed 230* with PoP. i usually baked for a couple hours with the oven cracked at 210 or so. then lay them out on news paper/paper towel for a couple days. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted September 23, 2011 Report Share Posted September 23, 2011 (edited) OK then, on to sealing. I am not sure on the drying times, but the first coat really soaks into the plaster, which is the whole point. So the first coat needs longer to dry. I hope you get feedback from someone who uses the Elmers method. I just wanted to say don't rush the process and certainly don't try to dry the Elmers in the oven. The Elmers will blister, ask me how I know. SHK is right. Be careful with temperature. Everything is OK until all the water has evaporated, but then the mold temperature rises to the oven temperature. Then if the critical temperature is reached, the PoP reverts back to its original structure and will become weak and powdery. Dave Edited September 23, 2011 by Vodkaman Quote Link to comment Share on other sites More sharing options...
chachybaby Posted September 23, 2011 Author Report Share Posted September 23, 2011 k. will keep that in mind.. I notice everyone has a different opinion on the temp factor. I went off of longhorns tutorial, 325 for an hour, one hour per inch of thickness. The two halves still have a damp feeling so I knew they require more drying. they are laid out on the newpaper drying now Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted September 24, 2011 Report Share Posted September 24, 2011 Gypsum plaster/Plaster of Paris Gypsum plaster, or Plaster of Paris, is employed by mixing water with calcium sulfate hemihydrate, nominally CaSO4·1/2H2O. This is produced by heating gypsum to about 300°F (150 °C). 2 CaSO4·2H2O → 2 CaSO4·0.5H2O + 3 H2O (released as steam). When the dry plaster powder is mixed with water, it re-forms into gypsum. The above was copied and pasted from Wiki, which although not a definitive source, is reasonably reliable. You should stay under the quoted temperature of 300°F. Dave Quote Link to comment Share on other sites More sharing options...
Pitbull Baits Posted September 24, 2011 Report Share Posted September 24, 2011 I would dry them on a rack. That way it drys top and bottom or lean them up on something to air out the bottom as well. Quote Link to comment Share on other sites More sharing options...
nova Posted September 24, 2011 Report Share Posted September 24, 2011 Gypsum plaster/Plaster of Paris Gypsum plaster, or Plaster of Paris, is employed by mixing water with calcium sulfate hemihydrate, nominally CaSO4·1/2H2O. This is produced by heating gypsum to about 300°F (150 °C). 2 CaSO4·2H2O → 2 CaSO4·0.5H2O + 3 H2O (released as steam). When the dry plaster powder is mixed with water, it re-forms into gypsum. The above was copied and pasted from Wiki, which although not a definitive source, is reasonably reliable. You should stay under the quoted temperature of 300°F. Dave Holy cow Dave; that's a lot of letters and numbers. It hurts my eyes;lol www.novalures.com Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted September 24, 2011 Report Share Posted September 24, 2011 I knew I should have trimmed away the fat on this one. We're only interested in the temps. Dave Quote Link to comment Share on other sites More sharing options...
chachybaby Posted September 25, 2011 Author Report Share Posted September 25, 2011 cool makes sense, nice to see the chemical equation behind the reaction between the water and PoP. So it can definately be reverted back to original form if too much water is released, or overheating to a point where too much H2O is lost Quote Link to comment Share on other sites More sharing options...
