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NJFishRGuy

First two piece mold but...

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My first two-piece plaster mold (a 4" stick bait) is in the oven drying. This is my second attempt, and it had the same problem as the first, only it was less severe. For some reason, the second half of the mold (the "upper" half) has air bubbles in it! :pissed: After my first experience, I made sure that the plaster was thinner and I shook/tapped it almost until it started to set up. I took it apart today and Presto!, more air bubbles. These aren't too bad and I'm hoping I can fill them before coating the mold. Any ideas on what to use to fill the holes? Did I read wood putty somewhere?

Any advice appreciated...

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I suggest you doing a search on "air" or "bubbles", etc. to find previous discussions on the subject. That's what I am doing.

Devcon is used by some to coat their molds. One person said he doesn't

bake his plaster mold. He just uses Devcon to coat them.

Regardless, it sounds like you will need to coat the mold with a sealant or

Devcon to help keep bubbles out of your finished bait.

Hope the search helps you. That's what I'm doing before I make my first mold. Good luck.

Muskie Bob

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Use Devcon or better yet a bar top finish to finish the surface of the mold. You can fill larger defects with epoxy/plaster dust mix, or use a thick epoxy..

For your next mold get a product called Airid, from Deep Flex molds. You spray it into the mold just before you pour the plaster. Really keeps the air bubbles out. If you can't wait for your Airid to arrive try spraying the mold with a fine mist of water before you pour. It breaks the surface tension to allow the bubbles to release.

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Bubbles cause bumps in the poured plastic, which might not be all bad. In fact, I've drilled shallow depressions the length of a worm cavity to create the bummpy texture. Reminds me of a worm that Mr. Twister made years ago.

I always liberally brush the worm with more oil before the final half is poured. (PAM would do as well and not affect the surface of the bottom half.)

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I always liberally brush the worm with more oil before the final half is poured. (PAM would do as well and not affect the surface of the bottom half.)

I tryed Pam with flour in a mold gave it an interesting texture almost leather-like. Probably wont try that again. Devcon smoothed it out nicely though. Make sure to add a bit of coloring to the epoxy so you know everything is coated. Koolaid works quite well. 8O

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Good ideas all... I may try the spackle at lunchtime since I plan to coat the mold later.

I did notice that the bubble holes were all around the baits I used as masters, and not one was more than 3/8" from the baits, so maybe it is the baits causing the bubbles. I'm going to try to fix this mold, and make sure I use worm oil to coat the next one I make.

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NJFishRGuy,

Are you adding water to the plaster of paris in a container?

Or plaster of paris to water in a container?

I can't remember which is which but one of those methods greatly reduces air bubbles in the mold.

So maybe you could try mixing it a different way and see if it gets any better.

Hope this helps,

Mickey

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NJguy make sure that you DO NOT seal the part of the molds that fit together only the bait cavity and the pour holes. If you seal the parts of the mold that fit together the moldes will not seal anymore and you will get casting flash that you will have to trim off. This will pretty much ruin the mold.

If you coat the mold before you bake it the sealer will just peal off as the water makes steam when you pour in them. It may take a while but it will peel off if you don't bake them good first.

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I'm adding water to the plaster... I just read somewhere that the best method is to add plaster to the water and let it sit in a mound for 3 minutes or so before mixing. I think it's called the mountain method, or something like that. I'm going to try that next time.

I did bake the mold before applying the sealant... thanks for the input, FishNFool.

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When I get any holes I just hit it with a second batch of plaster or durhams, use some dental picks to fill the hole and smooth the area out. A lot of imperfections, as mentioned, can be covered with devcon. I am one of those that doesn't bake his molds. I just slap on the devcon and have had no problems with any so far. Have poured with them for a year now. I find the plastic worms demold just fine with no vasoline or lubricant. The only time I had some dificulties was with making a "zipper" worm. Had to do a little patch work but only a few minutes worth. You can also make a make shift vacuum chamber with your shop vac to help remove any bubbles from the mix. I end up mixing mine a little thin to help also. Slap it a few times against the counter to help knock bubbles out. I will also "paint" the plaster/water puddy onto the lure if it has detail or ribs with kids brush before pouring.

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Does the air bubble problem have something to do with the slightly uncured plaster or putty? Because it doesn't seem to matter if I glue baits down and pour over top, or pour the plaster or putty and push the master into it, my first half comes out terrific. Then, no matter what I do for the second half, I get air bubbles. Has anyone tried to press the first half down into wet plaster or tried sealing the first half then pouring over that?

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Travis,

Thanks for the suggestions... I'll try them next time around. I just finished making some pours with the mold I made (4 inch stick) and they came out OK. I'll have to make some more molds and give them a try. I did bang the heck out of it to loosen any bubbles while making the mold.

By the way, your molds look great and have awesome detail!

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I forgot to mention on two part molds I make sure to put a good coat of vasoline as filler in the bottom half of the mold. Then press the worm back in and clean up any vasoline that squirts out. This makes sure no air is trapped to escape into your upper portion when you pour it.

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I do the same as Travis by glueing the bait back in the mold with vasoline, but for the mold release, oil works better to get a bubble free top half of your mold. I only use Durhams for my molds it costs a little more but make a mold thats 10 time better and stronger. They come out very smooth if you oil the mold down good, mix the Durhams like thin pancake batter and tap the mold box good after you pour. I just got done making a swim bait mold that turned out perfect using this method. Here is the swimbait mold I just made. It's a 10" swimbait. If you will note I just drill 5/8" holes into the bottom half of the mold for my line up pins. I drill them just past the angle on the bit so it plugs right into the other half. Then when you pour the top half it makes the pins. Make sure you cut your pour hole before you bake this stuff, as after it is very hard to work with.

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What works pretty good for me is taking a small soft bristle paintbrush and spreading the pancake batter on the bait in a thin bubble-free coat just prior to dumping the rest of the batter on top of it. Also let the batter sit for a few minutes prior to pouring, tapping on the mixing container prior to pouring, and again tapping on your mold container after pouring.

here is a 5" Senko mold I made two years ago. It is coated with the blue mold-making silicone which works pretty good, but I'm looking forward to trying the thinned Devcon that everyone talks about here - should be easier and much less costly.

See ya on the riv' - TD

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Wow, your Senko mold looks awesome! That's what I was going for, but with a 4 inch. (I have an aluminum 5" stick mold.) Brushing the plaster on is another good idea.

What's the purpose of the odd shaped reservoirs above the worm? Just an attempt to get more plastic in the reservoir so you don't have to add more after the first pour?

For coating this mold, I used a material that SenkoSam had recommended. It's called Decorative Effects by Valspar, Gloss Clear Protector Gloss, P/N 93789, 100% Acrylic Latex. It's available in Lowes, and is designed to provide "a durable seal finish on walls". I paid about $5.50 for a quart. I used it on this mold, and was pouring one hour after coating. It goes on thin, dries fast, and cleans up with WATER!

I have used epoxy to coat a one piece mold I made. I found it a pain to apply and to keep thin, but the final finish was excellent.

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The reservoirs were made out of the head of big Kalins Mogambo grub, I put them in at the same time I put the "Sink-O's" in. You can use anything or drill them out afterwards like I read a lot of guys are doing. I place the "reservoir" piece about an 1/8" from the head of the bait, then when you pull the final mold apart you have very little material to drill or cut through to make the final reservoir/bait connection.

I also made a couple of 4" molds, I actually pour/use more of them than the 5". The aluminum molds are awesome, I don't have any of the 2-piece yet but recently got the brush hog imitation and love it. I also really like the looks of the fatter style senko imitations. Makes me want to take a second mortgage and buy a CNC machine :D

I'll try the Valspar, sounds great with no mixing, water cleanup, and best of all almost immediate pouring. My patience runs thin and I hate the waiting process - that's also the beauty of Durhams.

See ya on the riv' - TD

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