I am confounded by an inability of both polyurethane and Behlen’s Rock Hard table top varnish to adhere to some nightstands I made 20 years ago. At that time I used a homemade oil/varnish wipe-on finish. I now would like to do a varnish finish completed with pumice and rottenstone. First I rubbed the pieces with naptha to get any wax residue off. I then brushed on a coat of Behlen’s varnish. It took three days to dry and could be easily scraped off. I decided to completely strip the pieces with the nasty kind of stripper and try a few samples. I should point out that the surface is pretty smooth, and has not been scuff sanded. Small applications of Behlen’s and poly both still scrape off easily, but at least the poly dries in 24 hours.
Any thoughts?
Hans
Replies
It sounds like there is some sort of contamination on the surface. Many strippers contain a wax to keep the stripper from evaporating too fast. To remove this wax, wipe the item down with mineral spirits and wipe dry with paper towels keeping a fresh face on the paper towel.
Now, sand the surface using 220 paper. Dust and apply your finish.
A couple of things to remember.
Oil based finishes become dry to the touch when the thinners evaporate but they are no where near full adhesion and hardness. It can take up to 4 weeks to become fully cured and any attempt at "finishing the finish" should not be attempted until the finish is fully cured.
Varnishes, particularly poly varnish, does not take to rubbing to a high gloss. It never gets any glossier than it is right off the brush. Poly is actually fairly soft and the poly is added to resist scratching. Sanding or rubbing is scratching and poly varnish resists that. You can de-gloss by sanding but you can not work to a high gloss again.
Thanks,Howie.
I sort of figure there would be no way around re sanding the whole piece after these experiences. I have been using poly the last few months on some projects requiring rubbing out with surprising success. I have been bias against it for decades , but decided to give it a try on some tool handle re-finishing. I am not trying to get to a real high gloss. But the semi-gloss and smoothness from the rottenstone and pumice leaves a really nice finish.
Hans
Howie, my eyes still cross with many finishing questions, but I have a question -- a shot in the dark: Would a coat of shellac on the sanded wood help insure adherence?forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
ForestGirl,
You posted exactly what I was going to say.
It is an excellent idea to put down a seal coat of Shellac on this piece before your topcoat. You will have a hit or miss chance after you strip it to find out if you removed or cleaned all the residue. A 1# cut of some "blonde" or "pale" shellac will be your best move here. Varnish/Poly will bond to a "dewaxed" coat of Shellac really well.
Cheers!Dark Magneto
Thanks, Forestgirl. I have some superblonde already mixed.Hans
Jamie, shellac sticks to almost everything including wax. Almost anything sticks to shellac. So, shellac makes a perfect seal or isolation film in addition to being a very fine finish in itself. Oh, if using a waterborne finish or oil based poly finish, be sure to use a dewaxed shellac. The thing you need to be careful of is when dealing with contamination, brushing the shellac on agressively can intermix the contaminates with the varnish. Not good. Best to spray but if you must brush, flow it on with minimal back and forth brushing.Howie.........
Hans, see Dark Magneto's post to me here. Zinnser's Seal Coat would work.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Another proud member of the "I Rocked With ToolDoc Club" .... :>)
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