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ark50000

Sealant For Pop Molds

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I have made my plaster of Paris molds and they turned out great. I am now in the process of making a two part injector mold. The only issue i am having is after i have poured the plastic, bubbles start to seep through the plaster mold. I know its not the plastic itself but rather the plaster mold. What should i use to seal it properly? I have tried five coats of clear nail polish and a gloss spray paint enamel. Neither have worked 100%. Both worked slightly but wore off quick. Should i maybe try Mod Podge? what do you recommend. Thank you !

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2 most used are epoxy thinned with denatured alcohol, or elmers wood glue thinned with water

I started using both (epoxy over the wood glue) and havnt had any problems yet

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I used Epoxy I bought at Home Depot. I thinned it out with denatured alcohol. Be careful it doesn't puddle on you when it is drying. The puddle will fill in ridges of a mold and you will lose the detail of the worm. Any alcohol spilled on rags went outside immediately- highly flammable. For aluminum molds I used high temp epoxy paint (500 degrees) bought at Walmart in the automotive section. The paint worked great and made the baits more glossy looking. I will be trying the paint on my Plaster molds someday.

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I use Mod Podge it works great.Never had to redo a mold. Just watch how you put it on. If you use a paint brush, you can get brush lines in the bait. I put on three coats

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I used 3 or 4 coats clear gloss spray in a can.. Let dry and go over it with 2 or 3 coats clear nail polish... Works good for me. I reseal with nail polish every 8 or 10 pours..

 

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Elmers Wood Glue thinned with water works great with one coat.  Mix 50/50, flood cavities, let sit a few minutes, brush out cavities with foam brush, brush onto rest of mold, bake at 150 until cured. Simple, easy, durable.

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I don't know about Gorilla glue. I tried a different brand from Lowes once ( Don't remember the brand. ) and the finish was dull and rough. Stuck with Elmers after that. Elmers is cheap, and gives a great finish every time with a single coat. 

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Be sure your POP is completely dry before you seal it with a glue/water mix, or you can get mold under the sealer, which will eventually fail.  Don't ask me how I know, but I am going to have to redo my rage craw mold next week!  The half sealed with diluted epoxy is fine, but I have to do both halves again, because I can't get the soft plastic masters to go back into the epoxy sealed side.  Grrr!!!  Hahaha

 

Edited by mark poulson

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Good advice Mark. Fully cured/dried molds is extremely important. I pop mine in the oven at 150 for several hours with the door cracked open a wee bit to dry them.

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I weigh my plaster molds on a gram scale. When the mold stops losing weight in the drying process then the mold is 'dry'. From personal experimentation; PoP loses weight at a constant rate, there is no gradual slowing down of the weight loss, so it is very easy to determine the dry point.

I mention this because over drying in the oven can make the mold powdery. A cracked open oven works well, but the ideal rapid method is a warm box with fan circulation. I used 3x 100W incandescent (filament) bulbs as the heat source. If you make a lot of molds, this simple wood construction oven is worth building.

Dave

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