SlowFISH Posted January 30, 2011 Report Share Posted January 30, 2011 Hey all... I've been spending a lot of time making POP molds lately trying to to get a technique that I like and works best for me. Some of my molds are open faced hand pours and I'm getting great result here with regular POP materials and either sealing with thinned epoxy or 50/50 Water to Elmer's blend depending on the amount of detail in the mold. (BTW thanks to all who have posted their techniques, it's really helped!!!) I've even been making some nice two sided molds for trick worms that pour nicely by hand. I just bought a bag of Ultracal 30 yesterday as I wanted to make my molds a bit stronger so I can inject (Basstackle Injector) without breaking the mold over time. While the Ultracal material is much, much stronger, I seem to be getting a lot more bubbles then I was with the standard POP. The set-up time for the Ultracal is much longer than POP (20-30 mintues compared to 5 for POP), so I was a caught a bit off guard by this as I'd expect it to have less air being trapped with the longer setup time. Anyone using Ultracal and getting good results with molds that have small details? (Like thin appendages/tails, small ribs, etc) With each mold I've been vibrating it for a good 3 minutes by placing it on my workbench and running my grinder... makes the mold vibrate and I can see the air coming up and out pretty quickly. I'm tempted to try a blend of POP and Ultracal to see if I can find a happy medium or strength and fine detail. Any suggestions? BTW.. I'm using a 32:100 ratio of water to ultracal by weight. I've read others using a 38:100 ratio... may try this later today to see if it helps as well. Thanks, J. Quote Link to comment Share on other sites More sharing options...
mark poulson Posted January 30, 2011 Report Share Posted January 30, 2011 It might be simpler to just make some wood boxes for your POP molds, with the sprue hole in the wood. They will last forever, or until you drop one too hard on the garage floor. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted January 30, 2011 Report Share Posted January 30, 2011 I did a test a while back, using my shopvac to create a vacuum. Even though the pressure drop is not that great, it did make a difference with the bubbles. It won't work for thicker liquids like RTV, but works for PoP. Easy to set up and might help you. Dave Quote Link to comment Share on other sites More sharing options...
SlowFISH Posted January 30, 2011 Author Report Share Posted January 30, 2011 I have a vacuum chamber that I can use, but found I was getting similar results without using it for standard POP. I may need to try it again with the Ultracal as it takes longer to setup and therefore should theoretically give it enough time to degass the air out. I'm gonna go try upping the mix to 38:100 now and see if it makes a difference. Plus I want to test what I need to do to seal it up as well. I will say though, this stuff is TOUGH... basically like concrete or grout to some extent. J. Quote Link to comment Share on other sites More sharing options...
SlowFISH Posted January 30, 2011 Author Report Share Posted January 30, 2011 Little update... Tried another mold with a 38:100 ratio mix... much better. To aid the process I poured 25% of the mold... tapped for a minute... poured another 25%..... tapped...etc until I filled it. So at this moment I'm pretty happy with the way it's pouring. I also sealed an earlier mold I poured with thinned epoxy.... one coat is all it needs as it didn't really absorb much, I'll try a Elmer's coat on the next one to see how things go. J. Quote Link to comment Share on other sites More sharing options...
rixon529 Posted February 2, 2011 Report Share Posted February 2, 2011 I'm tempted to try a blend of POP and Ultracal to see if I can find a happy medium or strength and fine detail. Any suggestions? I've never used Ultracal, but according to the USG MSDS for it - by weight, Ultracal is about 85% Plaster of Paris to begin with. The rest is about 10% Portland cement and 5% Crystalline silica. Hope this helps. Rick Quote Link to comment Share on other sites More sharing options...
SlowFISH Posted February 2, 2011 Author Report Share Posted February 2, 2011 I've never used Ultracal, but according to the USG MSDS for it - by weight, Ultracal is about 85% Plaster of Paris to begin with. The rest is about 10% Portland cement and 5% Crystalline silica. Hope this helps. Rick Thanks.... I know if was heavy in POP already.... you wouldn't believe the difference the 10 percent cement and a little sand makes.... it's like a concrete walkway, you can't break this stuff. I'm gonna mix a bit more POP with it to find a good blend where it's does what I want and has a bit more rigidity.... or I'll use it to repair my driveway!!! LOL!!! J. Quote Link to comment Share on other sites More sharing options...
wchilton Posted February 2, 2011 Report Share Posted February 2, 2011 I would try a thin layer of POP around the baits to eliminate bubbles and then as soon as it sets up pour the ultracal for the main part of the mold. Saw a video recently on making a mold of a clay sculpture and they started with really thin POP (extra water) followed by the thicker/heavier mix for structural strength. Quote Link to comment Share on other sites More sharing options...
Roger Linnell Posted February 4, 2011 Report Share Posted February 4, 2011 I've made over 30 injectable molds with the hard plasters, so I have some experience in this endevor. i've used ultra cal, hydrastone and settled on superstone. Superstone is pretty new, it has fibers in the plaster for exra strength and is the same price as the other stuff. I vibrate my plaster the same way, works great, but paint a print coat of plaster on the baits with a small brush before pouring the rest of the plaster in the mold, that eliminatesthe bubbles. One coat of elmers and water is all I use to seal. Quote Link to comment Share on other sites More sharing options...
Smallie Posted February 4, 2011 Report Share Posted February 4, 2011 38:100 ratio is what they recommend. I use a digital scale to get it right. I also use a handheld electric mixer to mix it for 3 minutes before pouring into the mold box. Put the water in a container, slowly drop the plaster in by hand and then let is sit for a few minutes before using the mixer on it. When you pour the plaster into the mold box, pour in the corner, not on top of the patterns. Quote Link to comment Share on other sites More sharing options...
Pitbull Baits Posted February 4, 2011 Report Share Posted February 4, 2011 I use Air-Rid you get it at the hobby stores. Its made for removing air bubbles off your master when you pour the pop in. So basicly its made for pop molds and castings. I started using it and it works great. Its around $5 a bottle at Hobby Lobby or whatever hobby store is by you. Its by the casting project stuff like make your own stepping stone and making hand prints for kinds in plaster. Quote Link to comment Share on other sites More sharing options...
Pitbull Baits Posted February 4, 2011 Report Share Posted February 4, 2011 Sorry forgot that Ultra stuff your talking about. Won't the sand make pits in the cavity? or lose detail since the grains of sand might be larger than the fine detail in the master? Quote Link to comment Share on other sites More sharing options...
SlowFISH Posted February 4, 2011 Author Report Share Posted February 4, 2011 Thanks for all the tips.... I like the idea of pouring a thin coat of straight POP over the master then back filling with the Ultracal. I've been able to get the bubbles out with the right ratio as that isn't a big issue anymore. I do weight everything by grams which makes it easy... 100 grams of ultracal to 38ml of water. I was hoping with the stiffer Ultracal that I'd have a much tougher mold that I could seal smooth, but I've noticed it doesn't absorb thinned epoxy or thinned elmers as well as the POP either. I'll try the POP over part then Ultracal back fill tomorrow... I have a injection mold I'm working on for a craw trailer. I'll let you know how it goes... hopefully by sat/sun it will be dried and ready to go. J. Quote Link to comment Share on other sites More sharing options...
Pitbull Baits Posted February 4, 2011 Report Share Posted February 4, 2011 Maybe you should try Thompson Water Seal Quote Link to comment Share on other sites More sharing options...
Roger Linnell Posted February 4, 2011 Report Share Posted February 4, 2011 Sorry forgot that Ultra stuff your talking about. Won't the sand make pits in the cavity? or lose detail since the grains of sand might be larger than the fine detail in the master? Sand? Hoo boy. Quote Link to comment Share on other sites More sharing options...
wchilton Posted February 4, 2011 Report Share Posted February 4, 2011 Sorry forgot that Ultra stuff your talking about. Won't the sand make pits in the cavity? or lose detail since the grains of sand might be larger than the fine detail in the master? Ultracal is a gypsum-based plaster (like POP) that sets up much harder...no sand in it, it's smooth like POP. You're probably thinking of the sanded plaster used for building exterior/stucco , which is a cement-based plaster and is different. While we're on the topic, I've been wondering if thinning Ultracal (like POP) would make it more porous. That's what happens with concrete...excess water makes it porous because the extra water evaporates and leaves voids. One issue would be whether/how much extra water could result in shrinkage and/or cracking, and the plaster would also be a bit lighter and not quite as strong. POP seems to be pretty tolerant to adding extra water so I'd bet that ultracal would be like that as well. I did a bit of googling the last few days and it looks like the best way to mix any of these plasters is to sift the plaster into the water slowly, allow it to set a few minutes to hydrate, and then mix gently to avoid getting bubbles into the mix. Some mix by hand but an electric mixing tool is ok if it's not run too fast. Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted February 4, 2011 Report Share Posted February 4, 2011 I mix by hand, nice and slow. I pour just enough to cover, then use a paint brush around the edges. After pouring the rest, my hand goes in again, to stroke the master to release bubbles. The method works for me. Recently I read that it was not a good idea to use your hand. This was a disappointment for me. I had noticed that after working with PoP that my skin was very dry, but no other problems that a dab of cream could not fix. Dave Quote Link to comment Share on other sites More sharing options...
wchilton Posted February 4, 2011 Report Share Posted February 4, 2011 Vodkaman, your method of hand mixing is one I saw suggested on some of the art-casting sites I found. They suggested to treat hands both before and after with moisturizer or light petroleum jelly to protect against the dryness. One CAUTION that should be mentioned is you never ever want to allow POP to set up while your hand is in it. It can quickly become very difficult to remove the hand and the plaster can heat up enough to cause serious burns. As long as people know that I'd think mixing by hand is safe enough. Quote Link to comment Share on other sites More sharing options...
