Making P.o.p Molds

[Rippinlips26]

What is the best way to make a two piece mold out of plater of paris? I've watched YouTube videos and haven't became successful yet.

[mark poulson]

Type plaster of paris in the seach box at the top right of this forum page.

[JRammit]

Most common is the "float and cover" method (what I call it)..... Basically press your master half way down into the plaster, let dry, cover with more plaster

Of course there are plenty of ways to mess this up... What problems are you having??

[Rippinlips26]

I think I've found everywhere to mess that up. I can't get the two piece apart just wondering how you do that. If there is an easier way

[CNC Molds N Stuff]

Hammer works.

[fshng2]

Maybe Pam cooking spray before 2nd coat of pop. Also maybe a light coating on master too.

[JRammit]

Pam will soak into the dry plaster... I use Vaseline.... First use a paint brush to carefully get it all around the master and the parting line (you don't want any on the master, or you'll have ugly swirls all over the bait)... Then use a paper towel to smear it over every inch of the mold face

You can spray the master with Pam if needed, to help with removal.... The type of master you use makes a difference too.. You can get away with more using a soft master, but there are a few more rules to follow if you're carving a hard master

Once both halves are dry, place a flat head screw driver on the seam and tap with a hammer... If you applied the Vaseline correctly, the mold should open right up

[mark poulson]

For my first half of a two part mold, I mix yellow carpenter's glue into my pop, fill my mold box, lay in my soft bait masters, and then put it in the oven at 170 for an hour+- to cure/dry out.  Once it's dried out, I clean up the surface if it needs it, and then I coat the mold half, with the masters still in the cavities, with diluted D2T, two coats.  I let it cure over night, spray the first half with PAM, and then do the same thing with my second half.

Once the second half has set, after I've pried the two halves, I put the second half into the oven.  Then I remove the masters from the first half, and coat the cavities with diluted epoxy, two coats, to make sure it releases well.

Once I'm ready to coat the second half with epoxy, I coat the open cavities at the same time.

For me, it's a three day process, or the epoxy stays tacky.

I spray my molds with PAM before each pour.

[JRammit]

Mark, I keep forgetting to add glue to my plaster... I still wanna try that

You always use soft masters right?... I thought about sealing my mold face w epoxy like you do, but I carve my masters from wood or PVC, and I'm afraid of gluing them in...... The Vaseline has worked great though!

[mark poulson]

I do use soft masters with pop molds.  With hard masters, I would uses silicone, or some other soft material.

I would be worried about gluing wood masters in with the epoxy, too.

[JRammit]

The general rule is "hard master = soft mold... soft master = hard mold"..... But if you wanna make your own designs, you can't carve plastisol, so your only option is a hard master..... I got tired of paying $30-$60 in RTV silicone for 3 or 4 molds (that doesn't sound too bad until you consider how many of those molds were failed designs)... A $15 bag of pop can make ALOT of molds!.... So I made due out of necessity

For those interested, it can be done.... There's just a few "rules" to follow, which I leaned the "hard" way (pun intended

[Roger Linnell]

Most common is the "float and cover" method (what I call it)..... Basically press your master half way down into the plaster, let dry, cover with more plaster

Of course there are plenty of ways to mess this up... What problems are you having??

I start out like this, but I take the master out after the plaster(I use really hard stuff) has dried and sand the surface flat, then I drill a couple keys in the surface. Next, I spay paint the surface and cavity with el cheapo enamel, while the paint is still wet, I put the master back in the cavity, the wet paint helps hold the master in place. When the paint is dry, pour the second half of the mold, the plaster wont stick to the paint. Next step is to clean the paint off with some acetone and seal, I use Elmers

[JRammit]

I start out like this, but I take the master out after the plaster(I use really hard stuff) has dried and sand the surface flat, then I drill a couple keys in the surface. Next, I spay paint the surface and cavity with el cheapo enamel, while the paint is still wet, I put the master back in the cavity, the wet paint helps hold the master in place. When the paint is dry, pour the second half of the mold, the plaster wont stick to the paint. Next step is to clean the paint off with some acetone and seal, I use Elmers

I like that... Why not use high temp paint and leave it on??..... 2 birds, 1 stone

[Roger Linnell]

I like that... Why not use high temp paint and leave it on??..... 2 birds, 1 stone

If the master is a soft plastic, it will react with the uncured paint and the paint wont dry for 23 years. I do use the hi-temp stuff now and then when sealing The main reason for the paint is to hold down the master and as a release for part B of the mold. POP might need 2 coats because it's so pourous, the Hydra stone I use is super dense, like me, just need one coat.

Edited September 12, 2016 by Roger Linnell

[Rippinlips26]

Two piece mold was succesful! Used thw vaseline and popped off great! Also found a way to do a P.o P onepiece mold for a slugo that will come out as a if it was poured as a two piece.

I use modeling clay as my master baking it for 20 Mins at 250 to get it hard. But curious also what would be the best master to use to get detail!?

Edited September 15, 2016 by Rippinlips26

[JRammit]

Glad you're seeing progress!

For the best detail transfer, you'd want a soft master.... I've tried carving ribs, lines, ect. into my hard masters.. The impressions left are so small that they are weak and usually break off when the master is removed

It's twice the work and twice the time invested, but you can make a silicone mold to capture fine details from your hard master.. Then pour soft copies to use as masters for a plaster mold... This also makes multi cavities an option

[Rippinlips26]

That's the problem I was having guses I'll just do the silicone next

[JRammit]

One more thing you can try, if you're the artistic type... Get some air dry clay, crayola makes it Walmart carries it

The air dry clay becomes soft again if you get it wet.. Like when you pour wet plaster over it..... It can be a little messy and tedious to clean out of your finished mold.. But it will not damage any plaster as you remove it

[Rippinlips26]

I've never thought of that! Need to try that the baking in the oven just takes to long for me lol. BTW how do you post pictures on here??

Edited September 17, 2016 by Rippinlips26

[JRammit]

For pictures in a thread, click "more reply options" then click "add attachment".... If using a mobile device, you'll have to click "full version" first

Make sure and read up on the rules first... Pictures just to show your work go in the gallery... Pictures for the purpose of asking or answering questions can go here in the forums

[JRammit]

I used the air dry clay for a long time, it works pretty well.... The advantage is best of both worlds, hard/soft master..... The disadvantage, you only get one shot, if you mess up making the mold, your master is destroyed in the process.....

And like I mentioned before, sometimes it's a real pain to clean it all out, keep that in mind when adding details, picture trying to pick and scrub wet clay off of them.... Still a viable option, and at $5 a tub not much to lose

[mark poulson]

I used the air dry clay for a long time, it works pretty well.... The advantage is best of both worlds, hard/soft master..... The disadvantage, you only get one shot, if you mess up making the mold, your master is destroyed in the process.....

And like I mentioned before, sometimes it's a real pain to clean it all out, keep that in mind when adding details, picture trying to pick and scrub wet clay off of them.... Still a viable option, and at $5 a tub not much to lose

 

Would adding yellow carpenter's glue to your pop so it is harder make cleaning out the clay easier?

[JRammit]

Would adding yellow carpenter's glue to your pop so it is harder make cleaning out the clay easier?

If the glue makes the plaster smoother than it might... Problem is, the clay master sometimes crumbles and parts can stick in the cavity... Other times it all pulls out in one piece

I think it's just the porous nature of the plaster.. It's not designed for making molds, it's designed for sticking to walls...... But we find ways

[mark poulson]

It will make the pop both smoother and harder.  

I have no idea of the exact ratio of water to glue.  It's probably about ten parts water to one part glue.

The amount of glue to water ratio will determine how smooth and hard.  I add the glue when the pop is clumpy, and keep adding glue until it is completely mixed, so I don't over-water it.  If it gets too runny I just add some more dry pop.  

[JRammit]

It will make the pop both smoother and harder.

I have no idea of the exact ratio of water to glue. It's probably about ten parts water to one part glue.

The amount of glue to water ratio will determine how smooth and hard. I add the glue when the pop is clumpy, and keep adding glue until it is completely mixed, so I don't over-water it. If it gets too runny I just add some more dry pop.

Then I think that's the ticket!.... Two heads are better than one!