Bear fat?

Question for birchbark canoe builders. What is the approximate ratio of pine resin to bear fat to charcoal for seam sealer?

 

Ah, Kemosabe, you ask intelligent questions. The answer is a little more complicated.
I suspect it depends on what type of resin you are using; pine, spruce, fir,... I have mixed whatever is available together, heated, then strained/squeezed through cheesecloth to get rid of bugs, sticks, needles. Pour into a large coffee can (about the amount needed to gum one modest sized canoe) for later use, or into a frying pan (I pillage them from neighbourhood recycling blue boxes, even though they shouldn't likely be there).

If cool and hard in a coffee can, reheat in a large frying pan and add 1 heaping tablespoon of 100% vegetable Crisco (this is what I was taught to use by 2 native builders), and stir well. I think it may take some experimentation to get the proper consistency. Let cool enough that it is still pliable enough that you can apply it with a stick.

In the film, Cesar's Bark Canoe, the "gumming" process begins at 46:40.
They don't show what or how much "fat" is added, but the consistency is pliable enough to work into a seam using a thumb.


I recall Steve Cayard favours peanut oil. Or was that Henri Vaillencourt?

 

Crisco,great! Now what am I going to do with this bear fat? I guess it’s good for boots. The resin is from lodge pole pine. I believe Henry used black mastic in a caulk tube, at least that’s McPhee said. Just goofing around anyway.

 

Lard has a chemical composition close to bear fat (high in solid saturated fatty acids). Crisco is basically the vegetable oil version that is chemically hydrogenated to resemble those saturated properties.

I wrote a post a long time ago about my experience with trying to gum...

https://paddlemaking.blogspot.com/2008/05/gumming-inside.html

The main technique was to slowly add the fat to your resin mixture, then dip in a piece of scrap bark. Dump the bark in cold water (to simulate your lake water) and then flex. If the bark cracks you need more fat; if the mixture runs off or is too greasy you need more resin. The bark should flex without the gum mixture moving/cracking.

Turns out it also depends on the seasonal variation. Don't want too much fat in the heat of summer or the mixture will run. I mixed a batch for my full-sized canoe in the crisp air of April and added what I thought was the right amount of fat. Then came a heat wave in August and this is what happened...



My takeaway is that you don't want too much fat, certainly not a 1:1 ratio.

 

And it looks like you added charcoal to the mix as well. I have seen recommendations for adding charcoal to limit the "slump" during hot conditions that you show.

 

Ferdy responded to my e-mail, "Too much fat". Well, duh!