It turns out the non-empty can doesn't *always* self-seal when you
take it off to clean the gun.
Fortunately I was doing this in the basement & had already put a piece
of scrap plastic down on the floor, & had a bin handy. (And I have a
spare bin, now in use. The photo is outside --- I waited till it had
all set before carrying it out through the house.)
I suppose I should've put "minor" in the subject, as expanding foam
The only losses from this one were the basement bin (actually the bin
from a shredder that died years ago) and the cost of part of a can of
foam. No carpet, clothes, hair or other significant damage.
You don't mean like this bloke?
Peter Parry wrote on the Subject of the Expanding Foam
A friend of mine once built a canoe. He spent a long time on it and it
was a work of art.
Almost the final phase was to fill both ends with polyurethane expanding
He duly ordered the bits from Mr Glasplies (an excellent purveyor of all
things fibreglass) and it arrived in two packs covered with
appropriately dire warnings about expansion ratios and some very good
notes on how to use it.
Unfortunately he had a degree, worse still two of them. One was in
Chemistry, so the instructions got thrown away and the other in
something mathematical because in a few minutes he was merrily
calculating the volume of his craft to many decimal places and the
guidelines got binned as well.
He propped the canoe up on one end, got a huge tin, carefully measured
the calculated amounts of glop, mixed them and quickly poured the
mixture in the end of the canoe (The two pack expands very rapidly).
I arrived as he was completing this and I looked in to see the end
chamber over half full of something Cawdors Witches would have been
proud of. Two thing occurred to me, one was the label which said in big
letters: "Caution - expansion ration 50:1" (or something similar) and
the other that the now empty tins said "approximately enough for 20
Any comment was drowned out by a sea of yellow brown foam suddenly
pouring out of the middle of the canoe and the end of the canoe bursting
open. My friend screamed and leapt at his pride and joy which was
knocked to the ground as he started trying to bale handfuls of this
stuff out with his hands.
Knocking the craft over allowed the still liquid and not yet fully
expanded foam to flow to the other end of the canoe where it expanded
and shattered that end as well.
A few seconds later and we had a canoe with two exploded ends, a
mountain of solid foam about 4ft high growing out of the middle, and a
chemist firmly embedded up to his armpits in it.
At this stage he discovered the reaction was exothermic and his hands
and arms were getting very hot indeed. Running about in small circles in
a confined space while glued to the remains of a fairly large canoe
proved ineffective so he resorted to screaming a bit instead.
Fortunately a Kukri was to hand so I attacked the foam around his hands
with some enthusiasm. The process was hindered by the noise he was
making and the fact he was trying to escape while still attached to the
Eventually I managed to hack out a lump of foam still including most of
his arms and hands. Unfortunately my tears of laughter were not helping
as they accelerated the foam setting.
Seeking medical help was obviously out of the question, the
embarrassment of having to explain his occupation (Chief Research
Chemist at a major petrochemical organisation) would simply never have
been lived down. Several hours and much acrimony later we had removed
sufficient foam (and much hair) to allow him to move again. However he
still looked something like a failed audition for Quasimodo with red
burns on his arms and expanded blobs of foam sticking everywhere. My
comment that the scalding simple made the hairs the foam was sticking to
come out easier was not met with the enthusiasm I felt it deserved.
I forgot to add that in retrospect rather unwisely he had set out to do
this deed in the hallway of his house (the only place he later explained
with sufficient headroom for the canoe - achieved by poking it up the
Having extricated him we now were faced with the problem of a canoe
construction kit embedded in a still gurgling block of foam which was
now irrevocably bonded to the hall and stairs carpet as well as several
banister rails and quite a lot of wallpaper.
At this point his wife and her mother came back from shopping......
Oh yes - and he had been wearing the pullover Mum in law had knitted him
for his birthday the week before.
Peter Parry. http://www.wppltd.demon.co.uk
Normally I do (following advice here, probably yours), but it was
getting a bit plugged up (only a very slow, narrow stream coming out,
even with the knob turned all the way) & I had a can of cleaner.
I wonder if part of the problem is storing the loaded gun in a dampish
basement, but (bearing in mind the photo of the leak) I'm not sure
where else in the house it's safe to store it.
I get the impression there is a bit of variability in how well these
things stay sealed over time, and also how long you can get away with
leaving it on the gun. With my (cheap nothing special gun) a week seems
ok. You may have do a bit of unblocking - but not usually more than just
slicing the glob of foam off the end of the nozzle.
The damp out to make it cure faster, but would not expect it would make
it leak any faster.
That was quite a dramatic leak - that's not going to be welcome
anywhere! Perhaps keeping it wrapped up in a sack or in some other
container (large Tupperware style?) would be safer.
The problem I'm having isn't leakage --- the gun seems to get plugged
up when not in use. It's just that the leakage photo would make me
nervous about storing the thing "above ground" in the house. A loose
plastic bag sounds good, then I could store it in a dry area.
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