Thoughts on Filler recipes

Jan Bloom

LOVES Wooden Canoes
Loss of white lead led to increased use of silex and or clay in dry powder form. Has anyone given any thought to the use of the micro balloon powders that are available and commonly used as filler in epoxy. These are air filled spheroidal shapes in various materials. The two that come to mind that may be of interest are glass and phenolic. Glass of course is silica the same thing that silex is only in a hollow ball shape. Phenolic is a water proof resin that is also used in some varnishes. Both are availble as "powder" and could possibly used as light weight bulk to a traditional linseed oil based filler. Those that are using latex based fillers and light weight spackle are already using silica micro balloons as that or something very similar is what is used as the filler. Anyway just some thoughts for consideration.
I've been using microballoons in my filler for years now. I've been very happy with it, and my clients report great results when they do their own filling. One big advantage is a gallon of microballoon filler is 5 pounds lighter than silica-based filler. Can't argue with that!
Pat has filled many more canoes than I have. But I will second his vote for micro balloons. I've used latex deck adhesive and micro balloons without any issues. So far my boats have survived barnacles and the salt chuck without any problems.
I used micro balloons in some filler a few years ago, and the only problem I had was the balloons kept floating to the top, out of suspension.

With a mach mixer it might not be a problem but I was just hand stiring it.

And yes. I saved something in 5-7 lb range using the balloons.

So how do you guys calculate the ratio of the balloons to everything else? It seems that by weight would be too much volume (defeats the purpose as well) and by volume is not how most recipes are calculated.

For example, the following recipe from the "Canvas Filler Recipes":

Reprinted from Wooden Canoe #16 (no lead)
43 ounces boiled linseed oil
21 ounces mineral spirits
34 ounces enamel paint
2 ounces Japan drier
6 1/4 pounds 300 grit silica
2 ounces spar varnish

How much balloons to replace the silica?

Sorry, just a retired pastry chef here...sometimes we cannot get past the exact recipe mentality.
I simply replace the whole volume of silica with a like volume of microballoons. I can't tell you what that exact volume is, except it's one medium-sized margarine tub, and one large yogurt tub, plus a dash more (it's too long since I figured the volumes out and I don't remember what that equates to!). So in your example, you'd probably use about 1 1/4 pounds of microballoons instead of 6 1/4 pounds of silica.
Thanks Pat. I appreciate your answer.

Sounds like a Savory Chef talking instead of a Pastry Chef. Try a tub of this and a dash of that with pastries and your cake is bound to sink...hope that doesn't happen with the canoe!:eek:

Anyways, I can vouch for your filler. I got a gallon a few years ago before I decided to try making my own. Excellent stuff.
Zutefisk - regarding your comment about latex deck adhesive and microbubbles as a filler: 1) do you have a preferred brand of deck adhesive?
2) where do you purchase microbubbles?
3) what is the drying/curing period before painting?
4) and finally, what do you use for paint, i.e. oil-based, latex, alkyd? or?

I'm in Vancouver (the Canadian one), just north of you, so your solutions would probably work well here if they've worked for you.
Thanks for your input!
Slightly off-topic, but with the loss of white lead as an anti-microbial material in the mix has any one found any acceptable substitutes that's not as harmful? I'm thinking of stuff like the colloidal silver and other additives for household paint.
GOT --

If you are looking for a fine finish, I would probably lean toward a traditional filler.

1) I picked up the deck adhesive at Seattle Marine and Fishing Supply - Humbolts. I was looking for lagging compound (Bakor) they pointed me to this stuff. It's got a bit of mildewcide in it, but I suspect a packet or two of the hardware store stuff would probably be equivelent. It was not especially easy to apply, I squeegee it on. Then spend a bunch of time swearing if I've missed a drip. (it doesn't sand well)

2) where do you purchase microbubbles? -- Any place that sells fiberglass and resin.

3) what is the drying/curing period before painting? A day or two I suppose. Best be careful if you varnish the interior after filling. Varnish solvents soften the filler. I've raised a few bubbles along the stems where a little extra varnish tends to build up and seep through to the canvas.

4) and finally, what do you use for paint, i.e. oil-based, latex, alkyd? or?

I've been using a latex primer from home depot with a bunch of light weight spackle stirred in to make it sandable, sometimes a second coat if I did an especially bad job filling... then 3 coats of rustoleum rolled and tipped.

I used latex porch paint on my first canoe, it has been tough, but it was a bear to get looking good because about the only way you can sand out a drip is if you freeze it with dry ice.
Great! Thanks for the info Zutefisk, and thanks to all the other members for their input as well. I've decided to leap in with a 2-part lightweight epoxy filler made by systemthree ( called Quikfair. The company is located in Auburn, WA, but I was able to find their products in Vancouver BC at Fiber-Tek.
The fairing putty, as they call it, has microballoons to keep it lightweight. I slightly bungled the beginning of the first coat by mixing too much epoxy for my first application - the epoxy in my container started to harden after 15 minutes and I got a few chunky bits on the putty knife scoring my coat, which I was also applying too thickly. After that, I only mixed about a cup at a time and had no problems with the application, using a 3" metal flexible putty knife, and working from the centreline down towards the gunwhales, i.e. following the curve of the hull rather than working lengthwise, which was another mistake I'd made at first. Like any process, it takes a bit of practise to get it right, but it wasn't difficult. The 1.5 quart kit would be just about enough for one coat of a 16' canoe, possibly exactly enough if I hadn't lost about a cup right off the bat due to mixing too much. Once mixed, the consistency is viscous enough to be spread easily, and it doesn't drip or run at all. I think with the smaller batches you get a bit more working time as well, as I suspect a larger batch reaches some chemical critical mass faster, although that's just a guess. Fifteen minutes is plenty of time to carefully apply a cup of the mixture, and a cup goes pretty far. It's ready to sand in three hours, and sands very easily by hand - except where I botched that first bit, which may require a power tool - or just a lot of hand sanding and a careful second coat. I'm thinking two thin coats will do it. Even after one thin coat and sanding, the canvas feels pretty smooth, and it definitely has a nice hardness to it. As these products are made for boatbuilders, I'm anticipating that the Quikfair will be flexible enough to not crack, but time will tell. I'll post photos and let you know how it turns out. I'm a complete amateur at this, so cross your fingers!

After getting the first coat of filler on the canoe and sanding it, I had to put the project on hold while the garage/ studio was built...which gave me some time to do a bit more reading about fillers, especially anything involving epoxy! Well, nothing like locking the barn once the horse is gone...I am now considerably more aware of the concerns regarding flexibility, possible rot, etc., so will be keeping a close eye on the wood components. My reason for using this microbubble fairing compound in the first place was about weight and durability - however, I certainly don't want to destroy the rest of the canoe to save a few pounds on portages (and I've done enough portaging to know why THAT was a consideration!). If on the other hand this was a big mistake, I'm a daft hand at replacing canvas, and once it starts raining here in British Columbia, there's plenty of time for that (time as in: why isn't there enough to do something right in the first place, but always enough to do it over?)
I have also recently come across the information in this forum about using gesso as a filler, which I had considered but had de-considered on the grounds that it was so obvious that surely someone would have tried it!? (Obvious to people in the visual arts, that is - not necessarily to canoe builders). If there is any more info on this process, including pros and cons, please post it!