Mold Damage Repair

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Posts: 559
Joined: Sat Oct 31, 2009 1:36 pm

Mold Damage Repair

Postby Archives » Sun Nov 01, 2009 4:09 pm

JCat
Registered: 08/27/06
Posts: 18
09/10/06 at 07:05 PM
Reply with quote #1

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Question: Over the course of the year, I've purchased many ancient molds off Ebay and went through a huge assembly-line cleaning process using the white vinegar bath, followed by a soft bristle and heavy scrubbing, and finally a soaping and complete dry-off. I also use steel cleaner/shiner for the outside base of the mold. I notice a few molds like the complete skeleton from Fright Factory has some strange discoloring on the skull (the completed object itself - not the mold) , and one of my mini-dragon molds body's had an awful dry-like discolored patch with tiny holes in the final model after removal from the mold. Are the molds permanently damaged, or do I go through another vinegar bath and simply scrub harder in those areas? Any advice would be helpful.



Oh, forgot to mention - these are not burnt spots because everything else I've tried so far had the nice solid rubber finish and I'm using Patti-Goop & Plasti-Craft (not ToyMax).

Archives
Posts: 559
Joined: Sat Oct 31, 2009 1:36 pm

Re: Mold Damage Repair

Postby Archives » Sun Nov 01, 2009 4:09 pm

omnichi
Registered: 08/10/06
Posts: 85
09/26/06 at 01:18 AM
Reply with quote #2

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Hi, I had meant to reply to your post earlier, but forgot. I've found that pouring Topper Superplastic into molds goes a long way to cleaning them out. I've only had one mold that stubbornly refuses to be cleaned by Superplastic. Usually the first casting comes out all grey from zinc oxides, but the second is all bright and shinny plastic.

Joseph

PS Dr. Goop and Retro-Hobbies both have Superplastic for sale. I always order a couple of bottles when I order regualar Goop. Superplastic also makes quite realistic bugs, carapaces all shiny, which will give you the Creepy Crawlies.

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Posts: 559
Joined: Sat Oct 31, 2009 1:36 pm

Re: Mold Damage Repair

Postby Archives » Sun Nov 01, 2009 4:10 pm

dr_goop


Registered: 01/21/06
Posts: 44
09/26/06 at 08:53 PM
Reply with quote #3

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If the discolorations you mention are grayish and the tiny bubbles seem to be in thin layer where the goop touches the mold then you have zinc and or aluminum oxides on the surface of the molds. The oxides will become embedded in the goop and also cause the goop (PVC) to break down and release a gas. I get this often with old molds that have not been used in a while.

The vinegar bath should have taken care of the oxides. Maybe you took off the top layer of oxide/goop and have a little left. I would let the mold soak in vinegar for a short time like 30 minutes to an hour and then wash and dry. After I do that the first castings always come out a little gray but after that they subsequent castings are usually fine.

Mattel seems to have contracted through different foundries at different times. Some of the old molds hold up well and never give me problems but some, I assume from the old foundries, used a cheaper/lower quality mold material that oxidizes easily.

I did some experiments with some additives a while back that give the cured goop a softer slippery feel and it left a light coat of oily additive on the mold. That might help prevent the oxidation from occurring between uses. As a guess, mineral oil might work, but I haven't tried it.


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