filler still sticky

[mccloud]

This time I made up canvas filler using the first recipe in the Knowledgebase. The paint base was Sherwin-Williams industrial enamel, which I had read in other posts had been used and worked for other restorers. After application of filler in the basement workshop during the winter, the canoe was hung from the floor joists where it stayed at 50 degrees or a bit higher, and low humidity, for over 3 months. Touching it occasionally, it seemed hard, but I took it down and went at it with a sanding block. Although it is 90% hard, I am finding numerous little 'sticky spots' where to outside millimeter comes off, as if it had skinned over and then did not dry completely underneath. I'm not ready to give up yet, and with summer coming, I'll set the canoe in full sun on some 90 degree days and hope that bakes it to hardness. But this sure slows the restoration process. Have others had this problem and do you have a better solution? Thanks for the help, Tom McCloud

 

[Dave Wermuth]

no, I've not had that before. Only thing I had go wrong was to have it crack as it dried because it was too thick and not rubbed in well enough, I think.

 

[Jerry Fruetel]

I've used Sherwin-Williams industrial enamel as the filler paint base on two canoes, without the problem you described. I'd be hesitant to apply paint or filler in 50 degree temps, but I don't know if that caused your problem. If the summer sun doesn't help, you might consider using a heat gun as a last resort. But do it carefully---I suspect heating the paint above 120 degrees or so might cause problems.

 

[Dave Osborn]

You might try putting the canoe upside down on horses and putting a warm light underneath for a week or so. Maybe a flood lamp....
I did that one time for a couple of days on varnish that remained tacky. Maybe the warmth will finish the curing on filler, too.

 

[1905Gerrish]

I realize that you said you got the recipe from the knowledgebase and I realize that there are more then one recipe there but just wondering if you added Japan Drier to the filler and how much if you did? Sure you used Boiled Linseed oil instead of regular Linseed oil?

 

[mccloud]

Followed the first-listed recipe from the Knowledgebase, and added the ingredients in the order listed. The recipe calls for 2 oz Japan Drier, and that is what was added. Both Japan Drier and boiled linseed oil were fresh cans from the local Home Depot. This gave a filler somewhat 'thinner' than pre-made filler I've purchased from Roland, so the next time I will leave out the mineral spirit until the last minute and adjust viscosity by adding just enough to get the 'thickness' right. Tom McCloud

 

[mccloud]

An update: over these past 3 months, every day I was home and the sun was shining, the canoe, sitting on a dolly upside down, was wheeled onto the asphalt driveway, and had a sheet of black plastic covering it. As an experiment I diluted Japan Drier in mineral spirit and painted a portion of the hull with it. It is now possible to sand the filler without taking divots out of it. I cannot detect any difference between the section painted with Japan drier and the area that did not get painted. So my advice to anyone with a 'filler not drying' problem is to not give up prematurely. Put the canoe in the sun and let it bake. Tom McCloud

 

[Rollin Thurlow]

Tom, I believe the basic problem is that the filler was not sticky but it just had not warm enough drying temps before you started to work on it. 50 degrees for 3 months is not really good drying temp for the oil base fillers. They'll skim over and just remain soft underneath until it gets some real good drying temps. The good news is that once they get the warm temps or some good baking sun, they'll continue to cure like they should. It just takes time!

 

[Larry Westlake]

I've posted on the two issues of linseed oil that won't dry readily, and 'forced drying' before.

Linseed oils marketed as "boiled" are completely unreliable to use until tested and verified. I believe there is a caveat on the WCHA recipes page about modern materials being different from 19th-century materials, and this should always be kept in mind. We are well post-Watergate now, and "people don't lie anymore, they just change the meanings of their words". The word 'boiled' on linseed-oil product labels has had its meaning changed - it doesn't mean what 'boiled' means anymore.
I have lately been using a product from Mohawk that is called 'polymerized' linseed oil. I suspect this is much like 19th-century boiled oil. It dries quite quickly, is tough, and has so far been very consistent from batch to batch.

For forced, or I prefer to consider it 'controlled' drying of oil-based filler in cold weather, I now use a plank with 25W light bulbs screwed to it, fitted with a thermostat. With this strapped into a freshly filled canoe, I can let my shop go down to freezing and still have the filler kept at a constant warmth for a month, cheaply. A nice thick quilt goes over the hull to save energy and prevent a steep temperature gradient through the paint/canvas composite that could cause condensation or other problems.