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finish problems
- Thread starter ryan34
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- May 16, 2005
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Not a lot to do but speculate with as little as you've given. Three most popular:
1) Differential absorption. Spalted wood, end grain, things like that suck in more juice than face grain.
2) Application errors. Get the flashlight out to check and see if you have missed spots with your rag or brush.
3) Inadequate surface preparation. The stuff wants "tooth" to stick, and if you're not using that same flashlight to make sure your paper or wool has dulled the old surface, it can pull away from a slick area by surface tension.
Any of these should have obvious appearances related to their cause.
1) Differential absorption. Spalted wood, end grain, things like that suck in more juice than face grain.
2) Application errors. Get the flashlight out to check and see if you have missed spots with your rag or brush.
3) Inadequate surface preparation. The stuff wants "tooth" to stick, and if you're not using that same flashlight to make sure your paper or wool has dulled the old surface, it can pull away from a slick area by surface tension.
Any of these should have obvious appearances related to their cause.
- Joined
- Jan 27, 2005
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- pbase.com
Poly is not one of the favorite finishes of many woodturners. As supplied, it is rather thick so it tends to set on top of side grain and can build up quickly after several applications. At the same time it seems to have an amazing propensity to soak into end grain ... and the amount of finish needed to fill the pores seems to be never ending. You can thin the poly 50-50 with either naphtha (fast drying) or mineral spirits (slow drying) to minimize the buildup on side grain, but it does not help the end grain situation. A solution that I have used in furniture making is to first apply a couple coats of a one-pound cut of dewaxed super blonde shellac (you need to mix it yourself using flakes followed by filtering to remove most of the last remnants of wax). Follow this with a 50-50 mix of poly using naphtha for a fast drying finish. The poly should be applied thinly with a rag and about six coats are needed to equal one coat of unthinned poly. If you do not use dewaxed shellac you will have problems with cloudiness and adhesion.
Bill
Bill
Poly finishes
I'd use a sanding sealer or endgrain sealer and then apply poly to it. That'll get you a uniform finish.
I'd use a sanding sealer or endgrain sealer and then apply poly to it. That'll get you a uniform finish.
Don't for get wood type. Some pines and exotics have either poor absorbtion at points or will actually soften the finish over time due to natural solvents in the wood.
Dietrich
Dietrich
Ryan
It looks like you found the solution. I tried a can of wipe-on poly back at Christmas. It took 6 or 7 coats to get coverage and eliminate the dry spots. A few more coats for good measure and I was done.
I am real happy with Minwax Antique Oil lately. It's available at my local Ace Hardware and seems to cover better than Watco Danish and offer much better shelf life than Formbys Tung oil.
My two cents worth
Frank
It looks like you found the solution. I tried a can of wipe-on poly back at Christmas. It took 6 or 7 coats to get coverage and eliminate the dry spots. A few more coats for good measure and I was done.
I am real happy with Minwax Antique Oil lately. It's available at my local Ace Hardware and seems to cover better than Watco Danish and offer much better shelf life than Formbys Tung oil.
My two cents worth
Frank
ryan34 said:
Ryan, if the form is not to complicated try this next time. Be it Minwax or General Finishes Arm-R-Seal(I've used both) sand the first coat in rather than wiping it on. Sand with 400G or higher till the oil gets looking dull and dirty looking and drags the sandpaper. Then wipe it down with a rag. Once it is dry, re-coat as normal(2 or 3 coats) I do the first coat on the lathe. The inside of a bowl gets done before I finish turn the foot. My standard disclaimer; It may not necessarily be the right way, only way or wrong way but it works for me.
- Joined
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Please do not use SiC (black) paper to wet sand your light woods. Does nasty things to the pores that even repeated solvent wipes can't reverse. If you're going to wet sand and slurry fill, use pumice and some oil. Cut coats of your final finish are a great way to seal, and shellac, with its grain-swelling water will make a good base faster than oil/resin finishes alone. You can use SiC paper after a good seal, but there are other options with less surprise potential.