Tube In Casting, Annoying Shimmer??

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philb

philb

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Midlands, United Kingdom.
Hi,

I've been done a far bit of Tube-In casting with the resin-saver molds.

I've probably cast 6 Sierra tubes and they all came out great, but on the last few I've had a few spots under the resin where there is a shimmer effect? I appears to be on top of the stamps/paper but under the resin?

All stuck down materials where allowed to dry for 24 hours, the thin CA coated and dried for 48 hours before casting. PR warmed in warm water, poured into mold. Left for 30-60 mins or so and then put into the Toaster oven at 50C for 20 mins and the left in as the oven cools, normally over night or at least a few hours before being demolded!

Now the only thing thats change over the time is the Toaster oven. Should I be leaving the molds overnight before separating the resin from the molds, or is a couple of hours enough? I always make sure the resin has cooled and is hard! Just wondering if is not fully cured internally without resting overnight? Or possibly too much MEKP?

Any advice or observation, gratefully accepted!!
PHIL

1_shimmer.jpg
 
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Had the same problem and finally figured out it was mold release contamination on the surface before casting. I make sure the outer surface of the tube is clean before pouring the resin and my problem went away. Hope this helps.

John H
 
The cause is really hard to pinpoint. What has happened is for a fact. The resin didn't stick to the stamps in that one area for some reason. What really helped me was reducing my MEKP to three drops per ounce. Seems to me that the hotter cure was causing some of my seperation issues. This was really frustrating when I was wasting snakeskin.
 
Cheers Guys, I guessed there something causing a separation, made I have Vaseline from the mold release on a finger, or too much MEKP or too early from the molds!

Next to try clean fingers, clean blank, less MEKP and longer cure time! These wasted ones are annoying, as they look great except maybe one 2mm spot!!
 
Ditch the mold release. It is not needed with polyresin and only adds one more variable to the edquation...oned more thbing to control.
Doa good turn daily!
Don

Sent from my Samsung Epic using Forum runner
 
I had this same problem a few times on my stamp pens. I found that making sure the ca was built up enough above any of the stamp edges and curing too hot caused mine. I ended up not using the toaster oven after a few of these and letting it sit overnight then toasting it for almost an hour to just take away the stickiness. I never used mold release.

Jorge
 
just an FYI ..
silicone molds don't (technically) need a release.. BUT it stops the oils
from being leeched out of the silicone so fast. So the molds won't last
as long without release.. but the casting will come out fine.
 
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