Pro Seal Experiment

[longline]

is in progress. There have been a lot of questions about this product, generically called Pro Seal, but most likely everyone is using Flame Master. Anyway...

My buddy building an RV10 had some PS left over, expires this month. I used it to attach a NACA duct on my 8. (My stock of PS expired in... 2010.) So I decided to find out if the old stuff would still "kick" off.

The just expired PS/activator set up, even in a hangar running about 40 degrees, though it took several days.

The just expired PS, using old 2010 activator, was not tacky after several days in the same conditions. It was not as firm as the previous example; it was the same color

The 2010 PS, using new activator, was still tacky after the same period of time in the hangar. It was definitely a lighter grey in color.

All samples were brought into a climate controlled 70 degree environment. After a day there the second sample (just expired PS/old activator) was very close to the newer PS in texture; I would use it on non-critical jobs like the NACA duct.

The third sample (2010 PS/new activator) is no longer tacky. It has a soft, rubbery consistency.

Will report any changes that occur over time.

[Bevan]

Tip,

Keep your PS sealant in the fridge from the day you receive it. Take it out the day before use to bring up to room temp. Once your tanks are done (with non-expired sealant) the remaining PS will linger in the fridge and technically expire, but you will find all kinds of uses for it. My can of 5 year old worked great. My other can of eight year old was just a little too stiff to mix with the activator.

Bevan

[longline]

found what I found: the old PS was almost too stiff to mix.

As an update to the experiment, after two days at 70 degrees the Old PS/new activator batch has continued to set up. At this point I would say that it is useful for some sealing inside the cockpit/wing root area. I would not use it in a critical area, but it does have some uses like caulking.

I opened a 15 year old can of PS (Flame Master) and discovered that the remaining contents had hardened to stiff putty... you could mark it with a screw driver head. There is definitely something to be said for refrigeration of PS, a friend had a refrigerator in his hangar just for this purpose.

[vfrazier]

12+ years in the fridge for my can and it still works just fine. I set it on the counter the day before I want to use it to warm to room temp. No problems.

Like others, I wouldn't use it on a fuel tank, but it's perfect for filling gaps, such as when installing your tip fairings, etc., etc. etc.

Love that stuff. 1001 uses.

[rv7charlie]

I've got some PRC (Desoto) brand that I bought from another builder; has a use-by date sometime in 2005. Has stayed in the freezer since I received it. I had a couple of leaks in some almost 20 year old tanks last year, and patched the leaks with it in Dec of last year. One is still doing fine. The other has a small leak again, probably due to me not getting the area completely clean when I prepped it for the repair. And I should say that both repairs were done on the *outside* of the tank (around the nose attach angle on the root rib).

When I use the stuff I just take it out of the freezer & mix what I need. I only mix small quantities at a time (usually less than a tablespoon), and it is room temp by the time I'm done mixing it. It looks and acts just like the 'good' Flamemaster I used when I built the tanks on my project airplane.

Don't do what I did or you'll die, and other disclaimers as appropriate....

Charlie

[longline]

on the experiment. New(ish) ProSeal will activate with any age of activator.

Properly stored Proseal has a very long useful life, measured in years.

If you do not refrigerate ProSeal you should not expect it to be useful past the expiration date on the package.

ProSeal that is not useful for critical sealing still has use for things like caulking or some other application that does not require the hard set that new ProSeal has.

All the ProSeal lost due to age could have afforded me a nice refrigerator for the hangar.