?s for anyone that uses pvc for molds

[micharms]

Do you post cure your castings? Do you post cure them in the pvc?

Thanks
Michael

 

[soligen]

I did a "post cure" by leaving them in my hot car - waited 24 hours after casting. Not in the PVC. The Car method is not recomended. I have no idea what kind of fumes off-gas.

 

[DozerMite]

I have never post cured... no reason to.
Just pour, pop out in an hour, and turn.

Don't put PVC in an oven. When it's heated, it gives off toxic fumes called Dioxins.

 

[jskeen]

I've poured pr in pvc many times, and it always got hard enough quick enough to knock out on it's own. Now if I wanted to turn immediately I would put in the toaster oven for a while just to be sure, but don't try it in the pipe. Not only is it poisonous, but the pvc warps when heated, and you have to make up a new set of moulds. DAMHIKT

 

[bitshird]

I've poured pr in pvc many times, and it always got hard enough quick enough to knock out on it's own. Now if I wanted to turn immediately I would put in the toaster oven for a while just to be sure, but don't try it in the pipe. Not only is it poisonous, but the pvc warps when heated, and you have to make up a new set of moulds. DAMHIKT

Yup he's right about that, also the PVC seems to start sticking after 7 or 8 pours, but a 5/8 dowel usually drives them out, Honestly I think your better off using Ron Adams horizontal round molds, you can get better color swirls that way, it's kind of hard in pipe standing on end.

 

[Craftdiggity]

I have never post cured. Like the others said...Pour it and pop it a couple of hours later. Depending on how they feel after I get them out of the molds I let them cure for a day or two prior to turning just to be safe.

 

[RAdams]

Yup he's right about that, also the PVC seems to start sticking after 7 or 8 pours, but a 5/8 dowel usually drives them out, Honestly I think your better off using Ron Adams horizontal round molds, you can get better color swirls that way, it's kind of hard in pipe standing on end.

woot woot!

Fred (Ptownsubbie) Just wrote up a deal on how to make the same thing, Only verticle, which takes away the "flat spots" in teh pearls and metallics. Vert. is the way to go! You could probably convert my tutorial to make verticle molds too!


I used to use PVC, but ditched it after too many problems. First being the fact that the heat from the setting resin will cause some of the pipe to bend, making it extra interesting getting the blank out. And as mentioned, after a few pours, teh blanks stick to the pipe worse and worse. If you knock them out, you risk damaging the fresh, somewhat fragile blank (you can ask me how i know this, I will tell you all about it!). So you would need to replace them regularly. CPVC is said to sure the heat warping problems, but it is more expensive, and would still get sticky after a while.

Silicone molds seem to be the way to go for single blank pours. NewLondon has the resin-savers which I hear are amazing. There are several tutorials in teh library for silicone single molds, and even multi blank single molds. The primary strengths to the silicone i think are: flexibility, easy to use, easy to make, last forever, fully customizable diameters, sizes, shapes, etc.

 

[micharms]

Thanks to everyone for the good info. I'm going to look at making up some silicone molds once I get some materials together. The casting I'm doing right now is for bottlestoppers. The split PVC worked better but by the time I do all the taping etc I've used a lot of time that could be better applied doing something else. When I get the blanks out of the molds (and it still takes some work to do that) They are still tacky on the sides as well as the tops and bottoms. That is after a few hours after pouring. Since it is hot but humid here am I just not using enough mekp to catalyze the reaction? Some of you say that you are able to pop them in an hour and go to work. If I don't post cure them for a while then it seems to take forever to get to the turning stage. The blanks turn well and look great when I finally do get them turned and polished.

Thanks again
Michael

 

[RAdams]

How many drops per ounce are you using?

I use 4 drops per ounce, pressure pot for an hour, oven at 150 for an hour, let cool and they are pretty much ready to go. I always let them set for a day or two at least but i guess they could be turned as soon as they cool off.

If you are pouring big stuff like stoppers, you might want to check out Curtis' tut on the cutting board mold. It os for pouring slab type pours, and may be handy for doing stoppers. Lots of choices out there for sure!

 

[bitshird]

For bottle stoppers I got 500 20 dram pill bottles from my pharmacist, they even have a depression in the center of the bottom and are a great size for stopper molds, also the PR pops out once it's cured, also you can see exactly how much of what color you have and where you can put what ever in for doing 3D molds.