bubble problem with plaster molds

[Dave V]

How do you deal with the bubbles in plaster molds?

I made a couple last night and tapped them on the table for a while and the bubbles kept coming. I thought I got most of them out but I have a feeling my new senko's are going to look like they have warts.

Thanks,

Dave V

[woodsac]

I have a feeling my new senko's are going to look like they have warts.

That's not a bad thing. Around here we call that 'Creative Texture' Try mixing slower. Also, which did you add first, the water or the plaster?

This is a great thread to get you pointed in the right direction:

http://www.tackleunderground.com/board/viewtopic.php?t=4782

[jm]

With the stuff I use, I measure the water and the powder, then add the powder slowly to the water. It will form a little heap over the water, and slowly take up the moisture. I wait patiently 2 minutes, then I begin to carefully stir it.

If the powder isn't lumpy, it'll stir into a smooth mass pretty quickly.

Then after that I cheat and vacuum de-gass it.

Put up a picture of the Senko Toads.

jm

[Dave V]

I add the water then spoon the dry plaster in and mix with a tablespoon.

I'll pour some senko toads tonight and will post probably 3-4 am. EST.

Maybe I'll setup a vacuum chamber to degas it. I was also wondering what other materials are good for 2 piece molds?

I was thinking of doing a modified Horny Toad mold and that will be 2 piece.

Thanks for all the feedback (Keep it coming)!!!

Dave V

[Bass1cpr]

I've had problems with trapped air bubbles it's frustrating to have a good mold ruined by a couple of air bubbles. I've gone to mixing the plaster wetter so the bubbles can rise easier I also try and smash bubbles against the side of the mixing cup. Another thing is I set it on top of a jewelry cleaner and let it vibrate helping the bubbles to rise. I've also set my mold box with the master on top of the jewelry cleaner started my pour and let it vibrate this really helps put a smooth surface on the face of the mold, and also helps to keep bubbles away from the master form. Sounds bothersome but it has worked for me. Just some thoughts for ya. Good luck.

[Dave V]

I don't have a jewelry cleaner but my dog snores a heck of a lot, maybe i can pour on her belly. :grin:

JM, can you post a pic of your vacuum chamber. I never heard of a Schroeder valve. I have a fridge that I'm throwing out. it works fine so I'll pull the compressor and set up a vacuum jar. That sounds like the deal.

Thanks,

Dave V

[woodsac]

I don't have a jewelry cleaner

Set it on top of your washing machine and throw it on spin cycle for about 15 minutes.

[Bass1cpr]

I don't have any jewelry so I have to use it for something. I guess I could use ot for cleaning spinnerbaits, wait I hardly throw those anymore. Naw crankbaits are clean enough. :-D

[Dave V]

I tried gluing the baits down, then pouring. What a disaster

I had the baits glued down good (I thought) but the plaster still got under portions of the baits and the mold came out bad. (But no bubbles)

I think 'll try the washing machine spin cycle technique next time.

I didn't pour any worms last night and I have a wedding a couple states over tomorrow, so I'll have to ponder it for a couple days.

[jm]

I asked my dentist how she mixes up dental plaster. They have a soft squishy rubber bowl, and a stirring device that vibrates. Between kneading the bowl, and stiring with the vibrator, they get all the bubbles. The vibrating table is a good idea.

Schroeder valve, the little thingie in a tire stem that keeps the air in. In refrigeration, we use a flare fitting (5/16" I think) with a schroeder valve built into it.

http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1611630309&ccitem=

I just drilled a hole in the top of a wide mouth canning jar lid, one of those without the threads, you use a ring with it. Then I stuck the extension tube of the schroeder valve through the hole and buttered it up good, inside and out with permatex RTV blue. That's how you connect to it with a standard refrigeration service hose. You don't need the ring, vacuum holds it on good.

The vacuum pump is plumbed solid into the refrigerator. You have to cut the tubes to get it out. Then you silver solder one of these fittings to each tube, and that's your pump. If you can leave long enough tubes you could maybe flare it out, or use compression fittings. None of that works for refrigeration, but should be good for the plaster deal. You need to leave the cap on the outlet pipe, just loosened a half turn or so, so it doesn't pump so much air through that it blows the oil out all over the floor, thus irrititating the CFO. (Chief Financial Officer, otherwise known as Sweetheart.)

You could probably just use automotive vacuum hose, and slip it over the copper tube at the pump, and one the same size permatexed into the jar lid.

Leave plenty of headroom over the product you are putting into the chamber. When the air comes off, it'll "boil" up some. Plaster goes about 30%, but RTV silicone goes at least 100%. Get it into the pump, and your goose is cooked.

jm

[jm]

Sorry, the Grainger link in the last is tied to a session, and will fail.

http://www.grainger.com/Grainger/wwg/start.shtml

Part Number 3X727

jm

[Dave V]

Now that I glued the baits to the pan, what removes superglue? Nail polish remover?

Thanks,

Dave V

[jm]

Dave,

I used the vacuum setup last night. Here's some pictures.

1. The pump

2. The vacuum jar

3. 100 ml of RTV in a 240 ml cup under vacuum.

hope it helps,

jm