Proseal tip

I found that putting mixed proseal in the freezer at -20?C reduces the setting rate almost to zero. I mixed 70g of it 10 days ago and used the last of it yesterday - it was still easily spreadable. The frozen stuff is just soft enough to dig out a lump of it, but if I need to keep the pot out for a while I put it in ice water. It's good not having to worry about the proseal going off while you're working, not wasting heaps of it and always having some ready when you get time to rivet something.

BTW, it works even better for 2-part epoxy primer - I did some spot priming with some mixed 3 months ago. It's neat to have some of that ready when you need it too.

Conor
RV-9A 90990 wings

Proseal

Be very careful about this. I would test this method on a piece of scrap first to see what the longer term effects are. I would also call the makers and ask them what they think of this method. There might be a time limit that proseal has to catalyze in or it may not cure at all. I'm no chemist, but I would hate to see you put togther your tanks and then find out later that this stuff is not curing all the way and having to start over, or worse, crash because it comes off and clogs your pickup tubes. I found that mixing small batches works the best anyways. I never did more than two ribs at a time before I cleaned everything up and either quit for the day or made up the next batch. Once you seal those tanks up, it's hard to make repairs later.

I understand your concern but it does harden up normally when brought to room temperature. The hardening is a chemical reaction and like most reactions the reduction in rate is vastly out of proportion to the temperature drop. Literally, everything happens in slow motion until you warm it up. The actual time that passes is not important as everything depends on temperature (except radioactive decay ). Of course, builders should satisfy themselves that it is OK, rather than take my word for it. I do it because my scales have a resolution of 1g and I can't accurately measure less than 6 - 7g of part B and it makes way too much for one session.

Sealer notes

ronoc74 said:

I found that putting mixed proseal in the freezer at -20?C reduces the setting rate almost to zero. I mixed 70g of it 10 days ago and used the last of it yesterday - it was still easily spreadable. The frozen stuff is just soft enough to dig out a lump of it, but if I need to keep the pot out for a while I put it in ice water. It's good not having to worry about the proseal going off while you're working, not wasting heaps of it and always having some ready when you get time to rivet something.

BTW, it works even better for 2-part epoxy primer - I did some spot priming with some mixed 3 months ago. It's neat to have some of that ready when you need it too.

Conor
RV-9A 90990 wings

Click to expand...

You are right....up to a point. Before the era of outsourcing, at McDonnell-Douglas, epoxy primers and proseal were mixed daily in an area known as the "Sealer Crib" and then distributed to the various assembly departments, stored in nearby very deep freezers till needed on the shop floor. The proseal was labeled A1/2, A4, B1/2, B2, B4 depending upon the engineering spec and/or desired cure time. In all cases, an expiration date was stamped on each tube of sealer or bottle of epoxy and this was usually less than week. I'm sure there was a good reason for the expiration date.

I too have mixed Akzo epoxy primer and frozen the unused portion to be used later. But in my experience, I found it good for up to a week or so before becoming obviously unuseable. But mine was stored in a refrigerator freezer which I suppose does not get as cold as a deep freezer.

Rick Galati RV-6A "Darla"

I certainly wouldn't try the primer in a spray gun after 3 months. I had it there so I dabbed it on a few spots and it did the job. I think the expiry time for frozen proseal is related to the amount of working time available after it's thawed, before it is too stiff to stick properly and/or squeeze out of the joint.