SlowFISH Posted February 10, 2011 Report Share Posted February 10, 2011 Hey all... Curious to know if anyone has a good technique for removing your master/part from a POP mold without damaging the top parting line edge (2 piece mold). I'm not talking about with soft masters... but with solid master parts. I've tried many ways but keep breaking/chipping edges which is real annoying. My masters are made of ABS plastic and painted/sanded smooth with auto primer. So I don't believe they are swelling or absorbing water/POP. I make sure to coat/wax them with McGuires parting wax (used for fiberglass mold making) before pouring. I also place draft on the edges of the masters, so I don't have undercuts or vertical walls locking it in the mold, but no matter what I try I can't get the parts out consistantly without chipping edges. So far the best method I've found is using a x-acto to "trace/scribing" the part separate the POP... then pry and prey... this seems to work sometimes, but many times I get chips and then have to fuss with trying to fill these small thin areas and then sand them flat while not making marks in the mold cavity. Just curious if I'm missing something obvious... letting mold dry for days, or trying to remove the part while the POP is still setting up/green (not solid, but not loose)... or as I figure, this is just life with making POP molds. Thanks in advance. J. Quote Link to comment Share on other sites More sharing options...
Pitbull Baits Posted February 10, 2011 Report Share Posted February 10, 2011 Try rubbing petroleum jelly where ever it is catching at. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted February 10, 2011 Report Share Posted February 10, 2011 Achieving a neat parting line is a very hit and miss affair, even simply being able to retrieve your master without damaging it, is a nightmare, as you found out (this is why a soft master is preferred, but sometimes this is just not feasible). This was too unpredictable for me, so I developed a technique involving a third step. It is a lot more work, but you might deem it worth while, I certainly did. The first pour is the extra step. I build a cone of soft modeling clay and sit the master on the cone. Set the cone in the pour box and pour just past the parting line. Bubbles are not a concern. When the cast has cooled. I remove the cone and push the master out of its cavity. The edges will fracture. This is of no concern. Thoroughly dry the mold. Sand the face back to where you want the parting line. Coarse sheet of emery (I use 80 grit) glued down on a flat plate and figure of eight motion. Fire up the compressor with a fine nozzle, for cleaning the emery. Finish off with a couple of passes on 150 grit. Heavy coat of wax, reinsert the master. Place in pour box and pour top half. Split the mold. Now any chips or bubbles in the first cast, are now positive and can be carefully cut away with a sharp knife. I prefer to remove the master just after the plaster sets. It is still soft and I can rock the master slightly to free it. Remove the master and thoroughly dry. A few passes with 150 grit removes any faults. At this point I cut in the locators with a spherical burr, no deeper than 3mm. It does not take much to locate the mold halves and the less intrusive your locators are, the easier your mold will split. The first half is complete and ready to pour the second half. I have not mentioned the pour hole/cone, this is upto you. This method gives a very neat and crisp parting line, exactly where you want it. The temporary cast can be used again for making multiple molds, without having to go through the whole process again. It is essentially your master mold. I told you it was long winded, but it does remove the stress and guess work. Dave Quote Link to comment Share on other sites More sharing options...
SlowFISH Posted February 11, 2011 Author Report Share Posted February 11, 2011 (edited) Achieving a neat parting line is a very hit and miss affair, even simply being able to retrieve your master without damaging it, is a nightmare, as you found out (this is why a soft master is preferred, but sometimes this is just not feasible). This was too unpredictable for me, so I developed a technique involving a third step. It is a lot more work, but you might deem it worth while, I certainly did. The first pour is the extra step. I build a cone of soft modeling clay and sit the master on the cone. Set the cone in the pour box and pour just past the parting line. Bubbles are not a concern. When the cast has cooled. I remove the cone and push the master out of its cavity. The edges will fracture. This is of no concern. Thoroughly dry the mold. Sand the face back to where you want the parting line. Coarse sheet of emery (I use 80 grit) glued down on a flat plate and figure of eight motion. Fire up the compressor with a fine nozzle, for cleaning the emery. Finish off with a couple of passes on 150 grit. Heavy coat of wax, reinsert the master. Place in pour box and pour top half. Split the mold. Now any chips or bubbles in the first cast, are now positive and can be carefully cut away with a sharp knife. I prefer to remove the master just after the plaster sets. It is still soft and I can rock the master slightly to free it. Remove the master and thoroughly dry. A few passes with 150 grit removes any faults. At this point I cut in the locators with a spherical burr, no deeper than 3mm. It does not take much to locate the mold halves and the less intrusive your locators are, the easier your mold will split. The first half is complete and ready to pour the second half. I have not mentioned the pour hole/cone, this is upto you. This method gives a very neat and crisp parting line, exactly where you want it. The temporary cast can be used again for making multiple molds, without having to go through the whole process again. It is essentially your master mold. I told you it was long winded, but it does remove the stress and guess work. Dave Thanks for the info.... I like the idea of pouring the second half and sanding it down a bit. I've been patching and then sanding the patches down which was working ok, but I'd then have to fuss around in the mold cavity which was real annoying. Your method sounds pretty good.... I'll give it a try. BTW... I've found wet sanding the POP is a good way to reduce dust and not clog the paper too bad if you use a good auto sandpaper and rinse it often. You do have to wait for your mold to dry a bit afterward, but makes sanding a bit easier. J. Edited February 11, 2011 by SlowFISH Quote Link to comment Share on other sites More sharing options...
Pitbull Baits Posted February 12, 2011 Report Share Posted February 12, 2011 They sell a sand paper for drywall. I got some at wal mart for $3.50 or so. Quote Link to comment Share on other sites More sharing options...
SlowFISH Posted February 12, 2011 Author Report Share Posted February 12, 2011 In the process of trying some of Daves advice/processes I think I came across a few things... 1. No surprise but petroleum jelly seems to be working better than the parting wax I was using... don't know why, but using the same masters I was having issues with are now releasing a bit easier... done with the wax... I'll save it for my fiberglass stuff. 2. Also this time around I started to pop the mold box open and pull the master out much earlier... basically once it sets up enough that you can't mark it with a finger, but can mark it with a finger nail I pop it out. I made two halves.... one chipped very slightly in two areas but much better than before, the other popped out almost perfectly one tiny flake that I won't even bother messing with it's so shallow. J. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted February 12, 2011 Report Share Posted February 12, 2011 I am very happy that you managed to solve your problem without having to resort to my long winded solution. I have read many times that it is recommended to thoroughly dry molds before removing the master, but this never worked for me either. I too have been using wax, but next time I do some pouring, I will give the petroleum jelly another go. The best solution is to use RTV for hard masters, but unfortunately, I have not managed to find a source locally, so I am stuck with PoP. Thanks for reporting back your findings. Dave Quote Link to comment Share on other sites More sharing options...
SlowFISH Posted February 14, 2011 Author Report Share Posted February 14, 2011 I am very happy that you managed to solve your problem without having to resort to my long winded solution. I have read many times that it is recommended to thoroughly dry molds before removing the master, but this never worked for me either. I too have been using wax, but next time I do some pouring, I will give the petroleum jelly another go. The best solution is to use RTV for hard masters, but unfortunately, I have not managed to find a source locally, so I am stuck with PoP. Thanks for reporting back your findings. Dave My first couple molds were RTV.... they are so easy to make as you an pretty much just suspend your master, pour around it, then cut one slit with a razor, pop the master out and start pouring. I didn't like RTV because i wasn't getting the "shine" I could get with a properly sealed POP mold. I made a few more POP/ultracal molds today... everything going pretty well... the technique thus far... Lube part with petroleum jelly 50% POP / 50% Ultracal - mix that at a ratio of 100g to 55g water by weight.... perfect amount of water to pour without bubble issues, dries in a decent amount of time. Wait till mold sets up where you can't mark it by pressing/hold, but can easily scratch it. Open mold and pop your master out... smooth any marks out with a small brush and water or a clay sculpting tool. Dry for a bit then fill any small marks bubble with POP... use a small brush to fill them and then a wet brush to smooth out remove the excess. Then dry completely and seal. I'd also recommend this with a soft master as well.... as you can carve/sculpt the mold face nicely with a little water and a sculpting tool to put the part/mold line right where you want it. This seems to be giving me some pretty nice molds. Once I get a couple sealed and ready to go, I'll see how they shoot. J. Quote Link to comment Share on other sites More sharing options...
Pitbull Baits Posted February 14, 2011 Report Share Posted February 14, 2011 Order some Airid from Hobby Lobby to spray on your master before you pour the pop in. I Use it never have any issues with bubbles since I started using it. It removes them and also makes your cavity a little more glossy before you seal it. Its pretty good stuff that I can't make pop molds without. Quote Link to comment Share on other sites More sharing options...
onlyonmonday Posted February 14, 2011 Report Share Posted February 14, 2011 Order some Airid from Hobby Lobby to spray on your master before you pour the pop in. I Use it never have any issues with bubbles since I started using it. It removes them and also makes your cavity a little more glossy before you seal it. Its pretty good stuff that I can't make pop molds without. Here is a search result. http://www.google.com/search?hl=&q=airid+mold+spray&sourceid=navclient-ff&rlz=1B3GGGL_enUS350US350&ie=UTF-8&aq=0&oq=Airid+mold+ Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted February 14, 2011 Report Share Posted February 14, 2011 Here is a search result. http://www.google.co...&oq=Airid+mold+ Who asked for a link? At least now you have learned how to use Google and will not be pestering anyone for links any longer. Dave Quote Link to comment Share on other sites More sharing options...
onlyonmonday Posted February 14, 2011 Report Share Posted February 14, 2011 (edited) Who asked for a link? At least now you have learned how to use Google and will not be pestering anyone for links any longer. Dave Now that is rude as hell.. Are you telling me I am NOT to be helping with anything to do with this site ?? Edited February 14, 2011 by onlyonmonday Quote Link to comment Share on other sites More sharing options...
nova Posted February 14, 2011 Report Share Posted February 14, 2011 Definition:- progress= man's ability to complicate the uncomplicated. I use and art brush and canola oil. Simply brush the first half with it making sure you don't coat the master; let it sink in for about 15 minutes and then pour the second half. I have never had a problem with this procedure. www.novalures.com Quote Link to comment Share on other sites More sharing options...
mark poulson Posted February 15, 2011 Report Share Posted February 15, 2011 (edited) Definition:- progress= man's ability to complicate the uncomplicated. I use and art brush and canola oil. Simply brush the first half with it making sure you don't coat the master; let it sink in for about 15 minutes and then pour the second half. I have never had a problem with this procedure. www.novalures.com Does the canola oil interfere with whatever you use to seal/harden the POP before you start pouring? I'm asking because I use thinned D2T, several coats, on my first half after I've oven dried it for an hour, without removing the soft plastic masters. Once the epoxy hardens, I spray it with PAM, with the masters still in it, and then fill my second half, and put the first half down on top of the wet POP. Then I turn them both over, tap the top with a rubber handled screw driver for a minute to get any trapped air away from the masters, and let it harden. Then the second half goes into the oven for an hour, and gets coated with the thinned D2T, too. I tried carpenter's glue, thinned, but the spray PAM prevented a good bond, and it peeled sometimes. I haven't had that problem with thinned D2T, but I like the idea of brushing on canola oil, since I think I'd get better coverage, so that's why I'm asking. Edited February 15, 2011 by mark poulson Quote Link to comment Share on other sites More sharing options...
nova Posted February 15, 2011 Report Share Posted February 15, 2011 Does the canola oil interfere with whatever you use to seal/harden the POP before you start pouring? I'm asking because I use thinned D2T, several coats, on my first half after I've oven dried it for an hour, without removing the soft plastic masters. Once the epoxy hardens, I spray it with PAM, with the masters still in it, and then fill my second half, and put the first half down on top of the wet POP. Then I turn them both over, tap the top with a rubber handled screw driver for a minute to get any trapped air away from the masters, and let it harden. Then the second half goes into the oven for an hour, and gets coated with the thinned D2T, too. I tried carpenter's glue, thinned, but the spray PAM prevented a good bond, and it peeled sometimes. I haven't had that problem with thinned D2T, but I like the idea of brushing on canola oil, since I think I'd get better coverage, so that's why I'm asking. I've used 2 part epoxy and the white glue wash(depending on how fast I want to finish the molds). neither of them have reacted with the oil. Like I said earlier, you have to make sure the oil has completly been absorbed into the plaster. It doesn't take a heavy coat of oil. www.novalures.com Quote Link to comment Share on other sites More sharing options...
mark poulson Posted February 15, 2011 Report Share Posted February 15, 2011 Thanks. 1 Quote Link to comment Share on other sites More sharing options...
Smallie Posted February 16, 2011 Report Share Posted February 16, 2011 <snip> I tried carpenter's glue, thinned, but the spray PAM prevented a good bond, and it peeled sometimes. <snip> I have used an aerosol mold release on my masters and found that it interferes with adhesion of the sealer. Now I only use mold release on RTV. Maybe the canola oil gets absorbed so deeply that it is below the surface? Quote Link to comment Share on other sites More sharing options...
onlyonmonday Posted February 16, 2011 Report Share Posted February 16, 2011 How about Mineral oil.. ******************************** Quote Link to comment Share on other sites More sharing options...
nova Posted February 16, 2011 Report Share Posted February 16, 2011 How about Mineral oil.. ******************************** Might be too thick although I've never tried it. Give it a go; that's how we learned. www.novalures.com Quote Link to comment Share on other sites More sharing options...
onlyonmonday Posted February 16, 2011 Report Share Posted February 16, 2011 I will not be doing a mold this week.. I believe also with Mineral oil is more pure that canola or ________.. It also is not thick.. 1 Quote Link to comment Share on other sites More sharing options...
nova Posted February 16, 2011 Report Share Posted February 16, 2011 I will not be doing a mold this week.. I believe also with Mineral oil is more pure that canola or ________.. It also is not thick.. There you go. Now I've learned something. I've never messed with mineral oil. www.novalures.com Quote Link to comment Share on other sites More sharing options...
onlyonmonday Posted February 16, 2011 Report Share Posted February 16, 2011 Does anyone know how linseed oil would work ?? Quote Link to comment Share on other sites More sharing options...
nova Posted February 16, 2011 Report Share Posted February 16, 2011 Does anyone know how linseed oil would work ?? Linseed oil has a strong odor. www.novalures.com Quote Link to comment Share on other sites More sharing options...
onlyonmonday Posted February 16, 2011 Report Share Posted February 16, 2011 Linseed oil has a strong odor. www.novalures.com Thank you all for being part of the brainstorming of this site.. Quote Link to comment Share on other sites More sharing options...
