Jump to content
ark50000

Sealant For Pop Molds

Recommended Posts

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 !

Link to comment
Share on other sites

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.

  • Like 1
Link to comment
Share on other sites

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
Link to comment
Share on other sites

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

  • Like 2
Link to comment
Share on other sites

On 3/17/2019 at 8:37 AM, Vodkaman said:

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

can you share more info on this? maybe a photo?

Link to comment
Share on other sites

Here is an isometric and a section through my simple pop dryer. the light blue shelf lifts out. PoP molds can be placed at the bottom of the box and on the shelf.

If you do a lot of molds, you could build a cabinet with lots of shelves. The holes above the fan is low pressure (fan blowing down) and so draws fresh air into the box. The holes below the fan are high pressure, so blow out wet air. Thus, moisture never builds up, maximizing the drying effect.

pop dryer 2.JPG

pop dryer 1.JPG

  • Like 1
Link to comment
Share on other sites

Here is a spreadsheet of the drying times. This was never intended for publication and so is a bit rough. But, it does give an indication of the drying process.

Contrary to what I remember; the rate of drying is not constant, but it tails off significantly at the end. You do not need 100% dry. Once the loss rate drops the mold is dry enough to use.

The molds sit on dowels so airflow reaches all surfaces.

Dave

pop dryer 3.JPG

Edited by Vodkaman
Link to comment
Share on other sites

17 hours ago, Vodkaman said:

Here is an isometric and a section through my simple pop dryer. the light blue shelf lifts out. PoP molds can be placed at the bottom of the box and on the shelf.

If you do a lot of molds, you could build a cabinet with lots of shelves. The holes above the fan is low pressure (fan blowing down) and so draws fresh air into the box. The holes below the fan are high pressure, so blow out wet air. Thus, moisture never builds up, maximizing the drying effect.

 

  

Quote

 

 

 

As Dave suggestions highlight in his diagram.... AIR MOVEMENT is key to drying and drying fast - heat helps - but if you trap in the moisture (ie. oven with door shut) you're just basically creating a sauna which doesn't really dry very well.  I've had good sucess just laying molds on a window sill that gets alot of sun and having a small cheapy fan blow over it... actually worked better than my small electric oven with the door cracked open.

Edited by SlowFISH
Link to comment
Share on other sites

SlowFISH is spot on, it is all about air movement. If I run my box without the lamps the drying time doubles, but to achieve this level of drying just by placing in a room would take a week or more. Another good place is on top of the refrigerator were there is air movement which reduces drying time to 3 - 4 days.

After all the testing I built a simple moisture sensor which beeps (very low volume) at different speeds depending on moisture, continuously once dry. So, no more weighing :)

Dave

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...


×
×
  • Create New...
Top