Jump to content

Expanding Foam prep


Featured Posts

Question for anyone who's used expanding foam:

 

I've just bought some cans of Soudal expanding foam (gun grade) for filling in gaps around Celotex slabs fitted for hull insulation. The directions on the can say to spray water on surfaces to help it cure. Not sure that I really want to do that in case excess water gets trapped. Am I worrying about nothing?

Link to comment
Share on other sites

22 minutes ago, Sir Percy said:

Question for anyone who's used expanding foam:

 

I've just bought some cans of Soudal expanding foam (gun grade) for filling in gaps around Celotex slabs fitted for hull insulation. The directions on the can say to spray water on surfaces to help it cure. Not sure that I really want to do that in case excess water gets trapped. Am I worrying about nothing?

 

I think a fine mist of water is advised to make the surface damp rather than wet. I also don't like the idea of this. Sprayfoam is mostly used on brick rather than steel.

I believe it will still set without water but will take a fair bit longer, it might not stick as well but that's not really a problem.

 

I need to do something related before too long, but I want it to stick directly to steel (under the cants). As you have a gun maybe you could do a few experiments and let us know what you find out?

 

...........Dave

Link to comment
Share on other sites

Just now, dmr said:

 

I need to do something related before too long, but I want it to stick directly to steel (under the cants). As you have a gun maybe you could do a few experiments and let us know what you find out?

 

...........Dave

Ta.

 

What sort of experiments do you have in mind? I bought a kit of 5 cans so may have a little spare.

 

p.s. on the internet, about half the price of similar Soudal kit from Screwstation.

Link to comment
Share on other sites

1 minute ago, Sir Percy said:

Ta.

 

What sort of experiments do you have in mind? I bought a kit of 5 cans so may have a little spare.

 

p.s. on the internet, about half the price of similar Soudal kit from Screwstation.

 

Squirt a blob onto a bit of dry steel and see how long it takes to go hard and confirm that it sticks reasonably well. It would be good to have confirmation that water is not essential.

 

It would be best to do this at the end of  some other project otherwise there is a risk of wasting an entire can of foam if the nozzle blocks.

 

............Dave

 

Link to comment
Share on other sites

It is thickness dependant, so a ‘thin’ foam layer will cure with humidity, but a thick layer will take a long time to cure if moisture has to diffuse a long distance.  On steel, I would wipe with a damp cloth to leave a film of water, then immediately apply the foam otherwise the water will have evaporated, when foam is applied, spray (plant mister) a little water on the surface.

  • Greenie 1
Link to comment
Share on other sites

16 hours ago, Sir Percy said:

Not sure that I really want to do that in case excess water gets trapped. Am I worrying about nothing?

 

Since the (small amount of) water is needed as part of the chemical curing process, I would think there won't be any excess water -- provided you don't apply it with a fire hose, of course.

 

1 hour ago, Idle Days said:

>>it helps the foam to expand fully<<

 

Exactly.

 

ETA: I've recently used this foam at home (on brick and concrete) and it swells up far more than you might expect!

Edited by Machpoint005
Link to comment
Share on other sites

  • 3 months later...
On 23/06/2021 at 20:01, dmr said:

 

I need to do something related before too long, but I want it to stick directly to steel (under the cants). As you have a gun maybe you could do a few experiments and let us know what you find out?

 

...........Dave

Sorry it's taken so long to get back to you; 1) about a good half an hour to go touch dry / stiff 2) yes, it'll stick, but the trick is to get it to stay in place initially while it cures. Careful, slow, progressive application might get you there.

Link to comment
Share on other sites

I never saw this thread earlier.

 

The fine water mist on the surface of whatever you're spraying it on is required to get the foam to stick rather than to get it to expand or cure. It's always expanded and cured whether the surface was damp or dry in m my experience, but without a damp vertical surface it can fall off before it expands and cures.

 

I think you were worrying about nothing. Even if some water did become trapped rather than being incorporated into the foam, a small, finite amount of water can only generate a small, finite amount of corrosion. 

Edited by blackrose
  • Greenie 2
Link to comment
Share on other sites

12 hours ago, blackrose said:

I never saw this thread earlier.

 

The fine water mist on the surface of whatever you're spraying it on is required to get the foam to stick rather than to get it to expand or cure. It's always expanded and cured whether the surface was damp or dry in m my experience, but without a damp vertical surface it can fall off before it expands and cures.

 

I think you were worrying about nothing. Even if some water did become trapped rather than being incorporated into the foam, a small, finite amount of water can only generate a small, finite amount of corrosion. 

And also, if the foam has sealed, then there will be no oxygen to feed corrosion.

Link to comment
Share on other sites

Possibly not relevant to OPs case but I once saw some steel discs left over from portholes being cut post spray foaming, some had been primed before foaming and some left unprimed, the difference was very noticeable, foam was easily removed from bare steel discs, in fact it came away in one piece while it was very difficult to get it off the primed discs (bare steel was dry and rust free) 

 

Lesson for me was to paint with a good quality primer before foam is applied. 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.