Blowing foam

Anybody ever experimented with blowing your own foam?  I’ve been doing a lot of work on my boat lately and I just ordered 4 gallons of 2-part pour foam.  I ordered extra so I should have some to play with when I’m done.

Some pretty funny stories about blowing foam in Greg Nolls book.

Exploding molds and what not.

I thought about using that stuff to fill a hollow wood board, I have a few hollow boards I would use more if they had foam in them.

Careful, that stuff expands way more than expected.

When I restored my sailbat, I replaced all the cabin marine grade plywood.

A buddy warned me to drill relief holes to let extra expanding foam a place to escape.

Glad I did.

It shot outta there in huge amounts.

Some areas still swelled up a bit.

A small cupful will expand to nearly a gallons worth or more.

You’ve been warned!

Thank’s Barry.  My 1982 23 Mako is under the knife right now.  It had a PVC fitting near the bow break and the foam down the center of the hull was saturated over time.  I’m almost done the fun task of digging the old wet foam out.  I will be refilling it the same way the manufacturer did in 1982.  I’ll be filling a space with about the volume of about 200 gallons.

Way back like about 1971, our shop teacher tried pour foam to make outrigger canoe ama’s. He learned how much force the expansion has the hard way. Be careful, get good advice so you don’t mess up your boat.

At work we have one of these:

It’s a tabletop unit that partially fills plastic bags with mixed PU that fully expands to fill shipping boxes.

The guys gave me a chunk to play with, about a foot square and 2" thick.

You have to have a really strong (and stiff) mold to get foam that has a consistent density. foam thats allowed to free rise not only has varying densities but usually has great variation in the size of the bubbles (voids), which is no problem if you’re just filling a space in the bilge of a boat, but it makes it a lot less practical if you’re going to sand into it as you would when shaping a board. 

I’ve done every job in the surf industry but blow foam and it seems to be the Xfactor. I’ve used Foss, Walker, Clark, some were from fiberglass molds and they invariably broke down aftertime, concrete is the answer, re-inforced with rebar, heating / cooling lines, but the barrier paper is where the real secret lies, combined with the mixing / pouring.

The cost factor for a home brew blank is prohibitive with what can and will go wrong, US blanks says the cost of each new plug is 5 grand and they still have problems as does every other foam blower, cut the nightmare and use seconds, they’ll be better than what a home grown blank could ever be

Plus… most pour foam isnt even close to the forumlas used for Surf Blanks

There is something pretty compelling about the thought of blowing your own blanks. I’m a builder so I work with concrete all the time. I reckon I could make a mold for about $300, this includes concrete, reinforcing steel, hinges, counterweights, o-rings and a system to clamp the thing together.  The actual chemicals are fairly cheap so once you have them the trial and error wouldn’t be too costly. If you got it right you’d be making blanks for $20 a pop.

At the end of the day it’s just a fantasy. The chances of ever making a decent blank are pretty slim. Like someone else pointed out there’s a reason why so few companies make blanks. It’s very difficult. Still, this could be a good retirement project. Having someone with industry knowledge would help a lot. 

…to make PU foam is easy; blow foam with the components that are just ready is even easier but to make quality White PU foam for surfboards is extremely difficult.

You know, still you see that the foam from USA is not the best; almost 50 years and still not the best chemistry; so is ok to mix couple of things to obtain Yellow PU like the one used in home building, or the heavy white one (too much pigment-also soft-) used for example on supermarkets ceilings, etc.

Regarding surfboard foam I have use, used or checked; even went to couple of factories: Clark foam from USA and from Brazil (yes, CF were made in Brazil from late 60s to about mid 80s; I do not remember right now); Bennet foam Brazil; Dion Australia; Dion/bennet Argentina (very soft); Surfblanks Brazil (teccel), USA; SA and Aust; Burford; Arctic; FJ Brazil (very bad foam intended to the favela guys-slums-); Safari from SA (worst foam ever); Elova foam; Oside foam; Rhyno (the same as Bennet Brazil); Walker; Pacific (second class formula from SB Brazil) and US blanks.


I took a whack at the sample foam from work. I am not used to not having EPS ‘beads’. This foam seems flexible and I can see it working great as packaging. Do rail bones from regular PU blanks bend or snap?  It’s skinned about 1/4 inch deep each side, had to use double sided tape to hold the work.