Expanding foam

[Andymsa]

Hi all,

 

i have tried a new a new method for terrain making using expanding foam, I won't go into the actual construction method. But with my old method I used a card formed into woven method and builders scrim glued to that and then mod roc applied on top of that. But I'm debating if to apply the builders scrim over the foam if so how do I fix it ( it's the old type that's not self adhesive) I hav tried an oiled based paint with the builders scrim apples when paint is wet. The the mod roc will be on top. But I'm wondering if I can just apply the mod roc over the foam directly and will it get a good key. Anyone have experience of using expanding foam.

[Dunsignalling]

Having used "Builders' Foam" a few times for (approximately) its intended purpose, I can confidently state that (a) it tends to expand rather more than one expects and (b) it finds gaps you previously didn't know existed.

 

Exercise caution.

 

 

John 

Edited May 23, 2019 by Dunsignalling

[Oldddudders]

2 minutes ago, Dunsignalling said:

Having used "Builders' Foam" a few times for (approximately) its intended purpose, I can confidently state that (a) it tends to expand rather more than one expects and (b) it finds gaps you previously didn't know existed.

 

Exercise caution.

 

 

John 

Eloquently put, John. The stuff clearly has potential for our use, but is about as predictable in its behaviour as the weather. 

[Rowsley17D]

I wonder if the OP is referring to expanded polystyrene or insulation board (Celotex) rather that the squirty stuff? I tried using that many years ago but it was useless.

[Andymsa]

I'm referring to the squirty stuff. I had good results with the shape of the terrine, yes I'm aware how it expands and using a gun definitely helps.

[Richard_A]

Plaster board fixing foam doesn't expand as much but still has the same stickiness.

[woodyfox]

I would suggest exercising some caution using the expanding foam. I've used it recently to fill some gaps in an outdoor building. It's nasty stuff and not too good for your health if precautions aren't taken. A quick internet search highlights some of the risks. Using it on a model where you are going to cut it, sand it and generally be near it for extended periods might not be too good for your health.

[Andymsa]

3 hours ago, woodyfox said:

I would suggest exercising some caution using the expanding foam. I've used it recently to fill some gaps in an outdoor building. It's nasty stuff and not too good for your health if precautions aren't taken. A quick internet search highlights some of the risks. Using it on a model where you are going to cut it, sand it and generally be near it for extended periods might not be too good for your health.

 

A good point regarding health, I'm not going to sand it unless needed and will be wearing a musk if I do aswell as a vacuum going at same time. I'm going to seal the underside of it and the top will be covered. 

[TheQ]

3 minutes ago, Andymsa said:

 

A good point regarding health, I'm not going to sand it unless needed and will be wearing a musk if I do aswell as a vacuum going at same time. I'm going to seal the underside of it and the top will be covered. 

Trying to attract others while sanding, is an interesting proposition..

[Harlequin]

I tried to fill a gap above some bi-fold doors a few years ago. The expansion was more than I expected (or the gap was smaller) and the stuff was dripping everywhere. I did my best to get rid of the excess before it set but annoyingly there are still bits stuck to the doors and to the clothes I was wearing to this day!

 

The note above about plasterboard foam seems very useful and I suggest using it in layers to avoid over-expansion, reduce wastage and to reduce the amount of cutting back and sanding needed. Putting more little bits of plastic into the environment is not good!

 

(I wonder if there's a some kind of organic expanding foam? Perhaps cellulose based?)

 

[Andymsa]

1 hour ago, TheQ said:

Trying to attract others while sanding, is an interesting proposition..

 

Lol, that's the autocorrect for you

[Andymsa]

1 hour ago, Harlequin said:

I tried to fill a gap above some bi-fold doors a few years ago. The expansion was more than I expected (or the gap was smaller) and the stuff was dripping everywhere. I did my best to get rid of the excess before it set but annoyingly there are still bits stuck to the doors and to the clothes I was wearing to this day!

 

The note above about plasterboard foam seems very useful and I suggest using it in layers to avoid over-expansion, reduce wastage and to reduce the amount of cutting back and sanding needed. Putting more little bits of plastic into the environment is not good!

 

(I wonder if there's a some kind of organic expanding foam? Perhaps cellulose based?)

 

 

Yes the expansion can be an issue, many forget that it can expand to double the size applied. Also those ones with disposable cans are an all or nothing affair. Using a proper gun is a completely different affair as you have so much more control