Poly not drying

[gsdoby]

I tried something different for finishing and it has not worked. Any advise on what went wrong. I put a coat of Myland's cellulose sanding sealer on a piece I turned while still on the lathe. I then took it off and put a couple of coats of wipe on poly over it. It has been a couple of days and has not dried. Should I not use wipe on poly over that sealer. The poly is old so I am wondering if age is an issue. I did this in my basement, which has worked before. Any thoughts or suggestions?:icon_scra:dontknow:

 

[JackLeg]

Humidity??

 

[Bas]

Oil- or water-based poly? Age can definitely be a factor, if it's older than three years it may no longer work. Temperature swings accelerate the aging.
The easiest test is to take a piece of scrap that doesn't have anything on it, apply the poly, see if it dries. If it does, it's your finish combination.

Good luck.

 

[5Etek-mike]

I'm still new to finishing, but have been doing research, along with some trial and error, and would like to offer some input. It may be possible that the sanding sealer didn't have enough time to cure prior to applying the wipe-on poly, and is not serving as a good catalyst for the poly coats. Here are a few other factors to consider in regards to the longer than expected curing times-

The type of wood- Natural oils in some woods such as Teak, Rosewood, Cocobolo, and Ebony are said to work against the the normal curing time for many varnishes and sealers.

The room temperature: Ideal curing for varnishes occurs between 70 and 80 degrees. You may need to find a way to slightly warm the wood surface to allow more oxidation to occur with the poly.

I was thinking humidity as well, but it seems that humidity be more of a factor with water-based finishes.

I would try giving the poly more time to cure, and warm the work area/ wood surface if possible to see if that helps. Do everything to control any dust from settling on the finish while it's still trying to cure. That's a great suggestion Bas! A great way to easily isolate the slow curing problem to either the poly itself, or it's interaction with the sealer :icon_thum

 

[gsdoby]

Thanks Bas. I tried a scrap last night and the poly dried OK so it looks like it does not work with the sanding sealer. The wood was Cocobolo by the way.

 

[Nice Figures]

I've tried the wipe on poly on Cocobolo several times and it never completely dries, it is always a bit sticky. We work in an air conditioned area so humidity shouldn't be much of a problem. It's the type of wood, to much natural oil.

 

[FuzzWuzz16]

I've never found anything that really dries on Cocobolo. If I use it, I leave it natural or a little bit of mineral oil to bring out color.

 

[Joe Scharle]

Wipe it clean with mineral spirits, to clean up what you've got now.
Wash the cocobolo real well with acetone then the poly will take. But don't wait too long or the oils will come to the surface again.
This has worked for me in the past.
Joe

 

[Howard Acheson]

Lacquer based sanding sealers should not be used if you are planning to clear coat with an oil based poly varnish. Lacquer sanding sealers contain stearates (soaps) to make the sanding easier. Poly varnish has relatively poor adhesion--it doesn't even want to stick well to itself--and should not be uses over lacquer based sanding sealers.

I would remove the finish using a chemical paint remover and start over. Either use a Myland finishing product over their sanding sealer or use an oil based sanding sealer compatable with an oil based poly varnish. Or, forget the sanding sealer entirely and use a thinned coat of you planned clear coat.

 

[ErnieM]

Several years ago I tried using Cocobolo for a harpsichord keyboard. Before applying wipe-on satin poly I wiped the cocobolo with acetone. The poly refused to dry. I ended up putting two coats of shellac on the cocobolo with no sanding at all. This sealed in the oils in the cocobolo and the subsequent poly dried more or less normally. To this day I've stayed away from cocobolo.
I do use ebony quite often and have no problem with the poly drying. On the other hand I no longer use poly for keytops - tung oil works better for me and avoids the plastic look I don't care for on keys.

Ernie

 

[Howard Acheson]

>> Several years ago I tried using Cocobolo for a harpsichord keyboard. Before applying wipe-on satin poly I wiped the cocobolo with acetone. The poly refused to dry. I ended up putting two coats of shellac on the cocobolo with no sanding at all. This sealed in the oils in the cocobolo and the subsequent poly dried more or less normally. To this day I've stayed away from cocobolo.

There are a number of oily tropical woods that should not be coated with oil based finishes. Cocobolo is only one. These wood species should be first coated with a barrier coat as you found out. Dewaxed shellac works well and SHOULD NOT BE SANDED or the barrier will be penetrated.

 

[ErnieM]

Thanks Howard. Although I use mainly ebony and sometimes walnut for keyboards I'm often tempted to use others. I assume rosewood would be on your list of woods that need a barrier coat. Which other species would benefit from a barrier coat?

Ernie

 

[Howard Acheson]

Hard to list them all. Many of the central american and south american hardwoods that are dense and oily are problematic.