Cracking paint over sealer - silicone, no more gaps, diagnosis and resolution

Forums › Home Workshop DIY › Cracking paint over sealer - silicone, no more gaps, diagnosis and resolution

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blakamin

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#1577417 20-Jun-2016 21:56

The cause of the problem is not only interesting and useful, it's a requirement.

Was the paint applied before the sealant had cured? Was primer applied before it was cured? Was it cured totally within temperature parameters or was it too cold at some point that caused the curing to take longer? All these things matter with the long term coating of paintable flexible sealants. We've just sent 5 boxes of a specialist sealant back to Germany as it was out of spec and waaay too thick, like it was out of date, but was well within its "use-by". We had the rep out and he agreed. I'm pretty sure we're not the only customer with a faulty product. At $180 a box, someone won't be happy.

I'm unlucky enough to have to play with this stuff daily. Preparation and curing are hugely important, so to find a solution, you need to know the cause.

Oh, btw, it's not silicone, it's a flexible sealant. Totally different products (try painting silicone) /pet peeve

timmmay

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#1577424 20-Jun-2016 22:17

The cause is of course key, but it needs to come from someone both the painter and window firm accept as independent experts. Opinions without facts are just conjecture. Ideas to pursue are welcome, but I imagine we'll have to get reps out, and I doubt they'll agree either.

Just trying to avoid paying for this to be done then redone.

Appreciate all thoughts and advice.

gzt

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#1577428 20-Jun-2016 22:26

Reps may well agree. Most common cause of issues is products not used to specification. ; ).

timmmay

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#1577494 21-Jun-2016 07:13

It may well be just an incompatibility. The key question is who spends the time / money to fix it. We have the painters resene rep coming out today, they're not independent as they want to sell to the painter, but at least they're a third party.

darylblake

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#1577495 21-Jun-2016 07:17

I found this out as well when we painted over some silicon sealer. (it wasn't really my fault but I couldn't pull out all of the sealer). It was the wrong type of sealer unfortunately.

The only thing that worked better than regular paint was when I painted over it with BIN primer. It never looked 100% perfect but we had tried a thin bathroom sealer and all sorts of different types of paint. The BIN provided the best result. It still wasn't perfect but it was significantly better.

Edit: Spelling

mclean

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#1577542 21-Jun-2016 10:28

timmmay: ....The sealent is claimed to be Bostik SafeSeal, which is meant to be the best possible silicone and will never crack. There's an idea that they may have run out and used no more gaps, which will often show this same behavior. It's also possible it's the paint that's cracked and the sealant is fine. I just have no idea...

A couple of points:

Nearly all silicone sealants you can't paint over successfully.

You should be able to paint over Bostik Safe Seal because it is NOT a silicone sealant.

Mighty Ape

Shop now at Mighty Ape (affiliate link).

timmmay

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#2183454 19-Feb-2019 09:59

The problem was eventually diagnosed as insufficient drying time for the filler. If you're using oil based paint you need to leave at least 24 hours for no more gaps to dry before you paint it, 48 hours if you use a lot of filler. Water based you can get away with significantly less drying time.

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