Craig Johnson
Lifetime member
Question for birchbark canoe builders. What is the approximate ratio of pine resin to bear fat to charcoal for seam sealer?
Bear fat?
- Thread starter Craig Johnson
- Start date
Rob Stevens
Wooden Canoes are in the Blood
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?
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?
OP
OP
Craig Johnson
Lifetime member
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.
Murat V
LOVES Wooden Canoes
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.
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.
Rob Stevens
Wooden Canoes are in the Blood
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.
Wouldn't hurt to ping Ferdy Goode on this topic - he's got a lot of experience with pitching canoes.
Rob Stevens
Wooden Canoes are in the Blood
Ferdy responded to my e-mail, "Too much fat". Well, duh!
Todd Bradshaw
Sailmaker
uuuuuh..... why does the post just above have a link to some sort of escort/prostitution listings? They may be very nice girls, but I doubt they know much about pitching the seams on a birchbark canoe......... Bye bye Bata.
Yes, another scammer has snuck in late at night with some inappropriate responses. They and their messages have all been deleted. I appreciate the tip and let me know if you notice any other odd or non-canoe related postings. Thanks,
Benson
