[[image:Expanding foam & tape tube extension 4661-3.jpg|right|200px]]
==Uses=* Fills gaps between sheets of rigid [[insulation]], to make the whole
layer draughtproof & insulating
* Fills holes where [[Plumbing|pipes]] go through walls
** [[cement]] mortar is a more traditional option
** Foam accomodates small amounts of movement
Insulates awkward to reach small spaces
==Types=Open cell versus closed cell, aka half pound & 2 pound foams
* Closed cell has more resistance to passage of moisture, insulates
more, and is stronger & denser
Some foams expand a lot, low expansion foam only expands a little.
Some come in a can with delivery mechanism, some are intended for use
with a separate better quality foam gun. After use the gun must be
cleaned out with solvent while the foam's still liquid.
Basic foams are flammable, and can produce toxic smoke in a [[fire]].
Fire rated foam gives fire resistance time.
==Gotchas=Things can go very wrong with expanding foam... [http://
www.diyfaq.org.uk/humour.html#foam canoe story].
The high level of expansion can catch people out, resulting in spilt
wet foam & damage.
Some foams generate very high forces as they expand /after/
solidifying. Misused as cavity [[insulation]] it can bring down
masonry walls with its expansive force. Don't fill enclosed spaces
with expanding foam, it needs expansion space.
The stickiness of the wet foam can be a problem, resulting in it
getting spread a lot unintentionally. Pay attention to stray wet foam
blobs. Put a dustsheet or newspaper down.
Set foam is too weak to give much support to solid [[filler]] applied
over it. Where this will be done, allow enough room for a good depth
of filler, and preferably reinforce the bulk of the filler with any
* plastic fibres
* added [[Adhesive|PVA]] or cement
or use [[sand]] & cement rather than filler for the bulk
==Tips=Damping the material its sprayed onto can help it set faster.
If a longer delivery tube is needed and nothing's to hand, an
extension can be made with [[Tapes|tape]], as shown in the pic above.
Protect the cured foam from daylight, UV degrades it rapidly.
Set foam has a mess of a finish, but is easily trimmed with a [[Knives|
=ìonomising=If money's tight:
* Use cheaper fillers where insulation isn't needed, such as
Cut sheet [[insulation]] to fit, rather than guesstimating. When
possible hold it in position and draw round with a pen to see where to
cut. Don't assume room corners are square, they're often not.
* Poke insulation offcuts or scrap expanded polystyrene into any big
gaps so less expanding foam's needed. Its easiest to inject some foam
then press the pieces in.
Sometimes gravity can be a pain, with wet foam applications
repeatedly falling out of position, wasting foam. Apply [[Tapes|parcel
tape]] to partially cover the gap to help it stay in place while wet,
then apply the foam behind it.
==Cleaning & Removing=Wet foam is sticky, drips a lot, and causes troubles.
===Skin==Nothing removes set foam from skin other than determined scratching
and peeling. If you ever wondered what waxing feels like, this is your
chance to find out. Trouble is it takes lots of small tear-offs, and a
lot of scratching, so expect the skin to look red for several days.
Its not too evil, but avoidance is only sensible. Get all you can off
before it sets! Lightweight gloves are recommended.
===Clothes==Its tempting to scrape the wet foam off, but don't. This pushes the
remaining film of foam into the cloth, making it impossible to remove
later. The result is ruined clothes. Remove the clothing and leave the
wet foam to set untouched. The whole lot should peel off later leaving
a clean result.
==Êrpet==Same principle applies to [[carpet]], prevent anyone treading on it
and let it set. That way you minimise penetration into the pile, and
can get the maximum amount of removal in the end.
===Hard Surfaces==Wipe the wet foam off, or let set and peel off.
==Storage=Shelf life is shortish. Once the can is opened, further storage is
optimistic, but sometimes succeeds, especially with separate gun type
==Disposal=Left over foam can make fake turds for the kids. Don't move the nozzle
while depositing, keep it completely still, and dump the foam onto
polythene or newspaper. The can can go in the bin.