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M-F plastic turning yellow vs clear 1st time heated

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17 hours ago, Bassmaster Rick said:

I have found that with multi heats even when using heat stabilizer and using only 20-30 second heat cycles the MF plastisol starts to 'darken'.

I've found M-F to be good (if careful) for about 3-5 reheats in the microwave no matter what else I do... except....  

When I am doing a larger (1/2 gallon to a gallon) batch of plastic I'll preheat in the microwave, finish to full temp and full clear in the old Bear's Stirring System Presto pot, then turn down temp to what I like for holding (around 305), partially (not fully) reheat sprues, runners, and bad pours in the microwave, and add them back to the Presto pots to finish reheating.  That will work all day long.  Since I can dump the reheats in between blades I can keep shooting while they melt back fully by drawing from between two other blades.  

I think however most of us are lying to ourselves about how diligent we are with our reheats.  The reason I say this is recently Captain Tony Jackson from Fin Chasers was over at my shop.  (He was in Yuma fixing some airplanes.  When ever he flies out we always go fishing anytime he can get away.)  We needed to make some of my favorite color Curly Buzz Frogs and Curly Buzz Frog Minis before our next outing.  I set him up back at the pouring bench with 4 cups of plastic, walked him through the first shot, gave him the schpeal about how to manage heat, and I left him making frogs while I went back in the office to finish the CAM on some custom molds.  When I made it back to the bench he had run the plastic down to the point where he was just reheating and he had to set the multi cavity molds out of the way.  He was just using only the single cavity versions.  I don't think there was enough plastic left when he was done to shoot more than one more CBF Mini.  I looked at the cooling tray and was surprised to see that I couldn't tell any difference in color between the first frogs and the last frog.  If the newest ones weren't still warm and resting on top there is no way I could tell.  I commented that I was pretty amazed and asked him how he did that.  He said he just followed my directions exactly.  

Short heats and stir to homogenize temperature EVERY time.  

Those frogs where white pearl with shad pearl flake.  I was out fishing with some from that batch (and catching) yesterday evening.  The last one was as white as the first one.  

 

Edited by CNC Molds N Stuff
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2 hours ago, Bass-Boys said:

need more than  5 drops in 8 oz. 

 try 10 drops ,, if not enough than try more next time .

use the yellowed plastic in green pumpkin or black baits so not to waste it .

 

I used way more drops and it was fine.  I basically put around 1 tbs in there for 8 oz of plastic to be safe lol.

I've reheated several times and no yellowing.  It was kind of worrying me because the stabilizer that I was using is orangish.

 

But yeah, I've been using the yellowed/orange plastics for dark colored baits.

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Thank to everyone who suggested the heat stabilizer. I needed to shoot a new mold just to try it out. Added heat stabilizer to my old (4 years old now) plastic and all was fine again. Reminded me of the old Calhoun’s when it was new. It went through 7 reheats and never saw an issue. I added more after the third or fourth reheat. I prolly used 1/2 teaspoon in 150ML. Between 1/2 and 3/4 cup. Here’s what it looked like.

 

Edited by Apdriver
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16 hours ago, Apdriver said:

Thank to everyone who suggested the heat stabilizer. I needed to shoot a new mold just to try it out. Added heat stabilizer to my old (4 years old now) plastic and all was fine again. Reminded me of the old Calhoun’s when it was new. It went through 7 reheats and never saw an issue. I added more after the third or fourth reheat. I prolly used 1/2 teaspoon in 150ML. Between 1/2 and 3/4 cup. Here’s what it looked like.

 

Those are beautiful!

 

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I have a gallon of LureCraft 60/40 blend plastic (#548) about 6 years old that was part of a 5gal bucket I broke down to 1gal jugs. Its been in my unheated garage since I got it, through temp ranges of -5F to 100F. When I broke it down I put a patch of plastic wrap over the mouth of the jug before tightly screwing on the cap.

Anyone have experience using old LC plastic? Should I expect a yellowing issue if I use this next spring?

Thanks in advance for any info.

Rick

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