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Thinning PRC

Old 17th Sep 2020, 07:52
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Thinning PRC

I've got a large quantity of out-of-date PRC to use on a Museum restoration. Is there anything that can be used to thin it? I've tried boiling the Semkit for half an hour in a water filled saucepan but it wasn't a total success.

Any suggestions for a thinning agent? Cellulose thinners is about 75% Toluene.

Thanks

Last edited by blue up; 17th Sep 2020 at 08:10.
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Old 17th Sep 2020, 08:40
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MEK was used as "thinning agent" many moons ago, not sure if it is "allowed"/acceptable these days. (Methyl Ethyl Ketone).
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Old 17th Sep 2020, 08:51
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Neat toluene will do the trick; I don't know about cellulose thinners but you've got nothing to lose by trying, seeing as you've got plenty of sealant. You'll need to be fairly quick if it's PRC B 1/2.

Last edited by stevef; 17th Sep 2020 at 12:25.
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Old 17th Sep 2020, 14:30
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Thanks. B 1/2 is what I've got here.

Nothing ventured, etc etc.
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Old 17th Sep 2020, 17:22
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MEK is still available, but as steve f say, toluene will do the trick.

All you have to then is enjoy the, erm, fragrant aroma .....as the mix takes place !
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Old 17th Sep 2020, 17:57
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And good luck in keeping your mitts clean to anyone who's never used PRC before!
Disposable glove fingers stick together like glue and you'll never get it off your clothes. Quite possibly one of the most disliked tasks in aviation. Hats off to tank teams.
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Old 17th Sep 2020, 18:40
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Ahhhhh....PRC. The aroma of freshly scratched anus. Fortunately I managed to avoid it in my 6 years of crash rebuilds. Being a metal basher had few privileges but avoiding sealant was one of them.
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Old 26th Sep 2020, 18:30
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Originally Posted by blue up View Post
Ahhhhh....PRC. The aroma of freshly scratched anus. Fortunately I managed to avoid it in my 6 years of crash rebuilds. Being a metal basher had few privileges but avoiding sealant was one of them.
PRC when out of date really does go "off". Had the unhappy experience of using out of date PRC to install a windscreen after two days it hadn't hardened just turned to chewing gum.

If you must use it then I suggest mixing a batch and making sure it hardens. Digging out the chewing gum is no fun!!!
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Old 26th Sep 2020, 20:42
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Originally Posted by blue up View Post
Ahhhhh....PRC. The aroma of freshly scratched anus. Fortunately I managed to avoid it in my 6 years of crash rebuilds. Being a metal basher had few privileges but avoiding sealant was one of them.

One must admit, one does not know what a freshly scratched anus smells like, but one must defer to your obvious experience.

faying every skin joint on a fleet of Jetstreams and a 125 was enough for me, had to mix the damned stuff by hand too.
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Old 27th Sep 2020, 18:10
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A few years ago PR1422 was withdrawn as it was deemed to be hazardous. I don't know what the hazard was but take care if this is what you have and use gloves as it is very hard to remove from the skin.
When I started in this game it was PR1422 and PR1422BT (Brushing Thickness) then it changed to PR1422A for the runny stuff and PR1422B for the thick stuff.
MEK is available mail order on ebay.
Mix MEK with the base sealant and then add the activator. As eric says, do a test batch.
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Old 29th Sep 2020, 21:48
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Originally Posted by dixi188 View Post
A few years ago PR1422 was withdrawn as it was deemed to be hazardous. I don't know what the hazard was but take care if this is what you have and use gloves as it is very hard to remove from the skin.
When I started in this game it was PR1422 and PR1422BT (Brushing Thickness) then it changed to PR1422A for the runny stuff and PR1422B for the thick stuff.
MEK is available mail order on ebay.
Mix MEK with the base sealant and then add the activator. As eric says, do a test batch.
& be very careful with MEK it's not nice to humans either by touch or inhalation.
But it's the only stuff that will remove PRC from your skin....
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Old 1st Oct 2020, 19:03
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Speaking of toxicity, MEK and toluene are fairly similar in terms of maximum allowed concentrations in the air (MEK has a slightly higher limit, but it's also slightly more volatile). On the other hand, the nasty effects themselves are more about long-term systemic toxicity for toluene vs. short-term irritating effects for MEK.
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Old 1st Oct 2020, 19:13
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I now use MEK for model making and try to have good ventilation. I must install that extractor fan in my mancave/shed.
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Old 1st Oct 2020, 21:21
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MEK.. But if the PR whatever that has gone off,will stay gone off.
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