Hi gang!
Finding what I would call the best finish for a call has been a research project of mine for over a year now. I am not interested in a fast finish, just the best possible waterproof durable finish to make a call last for generations. Any of you following my outdoor finish test on Facebook "Call Nutz" are seeing the results.
First of all I am completely sold on pure tung oil. Not the stuff you buy at the hardware store that is actually cut with petroleum distillates and is more of a varnish than an oil finish. Pure tung oil has been used to waterproof wooden boats in China going back 2000 years. Old school...
The process is tedious to do it correctly, but the results are worth the effort. Not for the production guys.
I have to get after Velvit Oil just a bit, as I see many people soaking calls in it, and my outdoor test shows it fails miserably. I once saw an MSDS sheet on it. Almost 50% vegetable oil, actually I hear soy oil, and the rest petroleum distillates. The distillates thin it enough for the soy oil to get into the pores and polymerize and seal the wood. Only water resistant.
That said, let's talk penetration of the tung oil into the wood. I do not sand past 400 grit so the pores in the wood remain open. I want it to penetrate deep down. To get that, I start with a 50/50 mix of pure tung oil and citrus solvent. Non toxic, food safe, smells great, and boy does it penetrate. Not unusual for it to bleed all the way through a call from the inside where the wood is just under 1/4 inch thick. Here is what I am using:
Not cheap, but a little goes a LONG way. I have done about 30 calls with this 16 oz. bottle. That's with around 7 coats per call.
So, I brush the call inside and out. You can see the wood soaking it up as you go, and the first coat really sucks it up. It will drip so you have to keep paper towels handy and catch them as it drips out. TAKE THE TOWELS OUT OF YOUR SHOP IMMEDIATELY AND DISPOSE OF EITHER BY BURNING THEM, OR PUTTING IN AN AIR TIGHT METAL CANISTER DESIGNED FOR OILY RAGS. YOU DON'T WANT TO BURN YOUR SHOP DOWN!! Please remember that these oil soaked rags are very combustible if left out in the air.
After 45 minutes or so, I come back and completely wipe the call down inside and out with old t-shirt rags. THEN I GO BURN THOSE RAGS IMMEDIATELY. Wait 24 hours and repeat the process. and again and again and again until the wood will no longer soak up any more. The wood will tell you as it will no longer have any dry spots when you come back to wipe it down.
Once I see the wood is completely saturated with the 50/50 mix, then I switch to the PURE tung oil. It is best applied by hand rubbing it in, and heating up the oil to thin it works best. I boil water on my stove, put it in a thermos bottle and head to the shop. Then I take a cool whip plastic container, and pour in about a half inch of super hot water. I put the tung oil in a baby food jar and set that in the water. Kind of like a double boiler. When the oil is almost too hot to touch, I brush it inside the call and then go back and dip my finger in the oil and hand rub it on the outside. It's actually kind of fun and smells good too. Same procedure, catch the drips, burn the rags, wait 45 minutes to wipe it down and burn the rags again. You can rub as many coats as you like until you are satisfied with the finish.
Then you set the call aside for a 30 day cure. The tung oil air cures and take 30 days to solidify. Note, you will get a little bleed out especially with burl wood, and you MUST go back daily and hand rub in any bleed out you see. if you do not, it will solidify on the outside of the call and leave a shiny spot that will stand out after curing. I learned this the hard way...
Once cured, the tung oil dries to a completely flat finish, so I go back and wax the call with this:
It has a great color to it, is inexpensive and available at Woodcraft.
Buff the call and enjoy.
It would be very interesting to see how far the 50/50 mix would penetrate in a vacuum chamber... ???
I hope this adds to the discussion, as I don't mind sharing what I am learning with all you call making buddies.