finishes

[Richard Avram]

I have a question about lacquer finish. I have been using wipe on poly for a piece that I am working on but I am having trouble getting the quality of shine that I want on the finial made from ebony. Is it possible to use a spray lacquer over polyurethane or will that totally screw things up? I suppose that I could research it but it is so much easier to just ask you guys. 😉

 

[Mark Mandell]

If the w-o poly is fully cured you should lightly abrade it with artificial wool (scotch-brite) vac off well, then apply your lacquer in light coats. That said, a few caveats:
1. Spray-can lacquer is very thin and builds slowly (much slower than the poly) so plan on a lot of light coats.
2. Lacquer, being an evaporating solvent finish rather than a reactive carrier/resin mix like the poly, will partially redissolve the prior coat. This gives 100% burn-in to form a single layered finish film, but you need to allow each coat to release its solvent before applying the next coat. Depending on temperature and humidity, this can take 2-4 hours. Apply too soon and you raise the risk of the softened film sagging.
3. If you're looking for a mirror/glass finish, plan on doing a fair amount of rub-out, but beware if you want to power buff as lacquer is very easy to melt and burn through with friction heat.

ps: I would wait at least 10-14 days from your last poly application before trying to apply lacquer. The poly needs oxygen to cure and the lacquer will cut off the poly film from access to the gas needed for polymerization.

 

[Bill Boehme]

That is not a problem after the poly has cured. I don't use poly, but I suspect that your technique might be more of an issue than the type of finish. Polyurethane takes a long time to cure. The surface will seem completely cured, but underneath it is still soft. The minimum cure time is a week for the surface before polishing, but I would allow a month if you plan to do serious leveling.

Lacquer is dry in a few hours, but I would wait a couple days at least before leveling the surface and polishing. Before spraying lacquer, if that is what you plan to do, you first need to fix the surface to get everything perfectly smooth. If deep v corners have varnish build up then that will also need to be taken care of before spraying lacquer. Use light coats to build slowly. To achieve the final smooth high gloss finish you will need to level and polish the surface with Micromesh or something similar. If your spray job is good enough then you might be able to go directly to a polishing compound.

 

[Richard Avram]

Thanks guys, here is what I have done. I used to use a high gloss poly but I didn't always care for the way it looked so I switched to a satin for most things and I like it better. After I read your posts I decided against trying the lacquer just yet and instead I used the high gloss poly. It was just what I was looking for and the ebony base and finial instantly popped. I'll give it one more light coat and then I'll post a picture.

 

[Gerald Lawrence]

lacquer over ?

According to the expert Bob Flexner you cannot put lacquer over anything except shellac. You could add shellac over cured poly and then lacquer, but i would rather start over if going to this extreme. Mixing finishes can get tricky and wind up with a mushy mess.
I notice you changed your mind, just wanted to add something from Flexner as I read it.

 

[Richard Coers]

I'm with Gerald. Except for the most dry dust coat, I'd be really surprised that lacquer will go over the poly without wrinkling it. I'd suggest you try it on a sample before spraying the finial. Shellac dries to a high gloss unless you want something tougher. Maybe a coat or two or shellac, then lacquer. As a side note, you can wet sand and polish wipe on poly if you give it several weeks to cure.

 

[Bill Boehme]

Just checked the Deft site and you are correct. This is interesting because we had an airplane that was painted with polyurethane and we were going to have it repainted. Nothing but methylene chloride had any effect on the poly.

 

[Mark Mandell]

Not to argue with Mr. Flexner, but I have used oil-based polyurethane as a sealer that was later topped with NC lacquer without incident. The poly was, as stated, fully cured, and I did not use a tie-coat of shellac. Interestingly, I was told by a refinish pro that the opposite, oil-poly over lacquer, should not be done on wood because the poly would be prevented from getting a good grip on wood fibers and would be likely to flake and peel. Never tried it so can't tell for sure.

All that stated, if my planned top coat was to be NC lacquer, there are better and easier sealers than oil-based polyurethane; dewaxed shellac being the primary candidate.

 

[Richard Avram]

I really appreciate all the good info that I get every time that I ask a question here. It always amazes me at how many turners don't take advantage of these forums. To have this kind of knowledge base at your fingertips and to be able to talk to people who are willing to share it is just invaluable. I went ahead and put on a couple of very light coats of a gloss poly and I'm much happier with the results. I'm including a picture.

 

[Mark Mandell]

I really appreciate all the good info that I get every time that I ask a question here. It always amazes me at how many turners don't take advantage of these forums. To have this kind of knowledge base at your fingertips and to be able to talk to people who are willing to share it is just invaluable. I went ahead and put on a couple of very light coats of a gloss poly and I'm much happier with the results. I'm including a picture.

Very nice, Richard.

Just a further note: Oil-based finishes, especially the polys, will "shrink" and pull the outside surface down closer to the wood until they are fully polymerized. What may start out as a dry coating 2-3 mils thick will likely result in a coating that's only somewhat over 1 mil thick, although the attenuated coating will be much tougher and more dense as the molecules of the film become more closely packed together over time. I mention this because you should expect to see some pores of the wood grain reappear in your gloss finish. Since Poly has the tendency to make a finished piece look like plastic, I view the very faint reappearance of the wood's grain as a positive effect.

Glad you got what you were looking for.

A final note: Non-gloss finishes ("semi" "satin" etm.) all start out as gloss finishes to which flattening agents have been added. The main result is, of course, the lower sheen, however the resulting optical quality and clarity of the coating is also reduced which will tend to "muddy up" your view of the wood grain and coloration. Because of this effect, I prefer to only use gloss finishes and then, if I want a lower sheen, use rubbing compounds to kill the shine but still keep more of the visual depth of the finish film.

 

[Mark Hepburn]

I really appreciate all the good info that I get every time that I ask a question here. It always amazes me at how many turners don't take advantage of these forums. To have this kind of knowledge base at your fingertips and to be able to talk to people who are willing to share it is just invaluable. I went ahead and put on a couple of very light coats of a gloss poly and I'm much happier with the results. I'm including a picture.

Off topic for this thread, but Richard that is a very good looking piece you turned.

Mark

 

[Richard Avram]

Okay, all this being said, here's another question. What is a good alternative to using poly? I have been using that almost entirely because I wanted to get comfortable with one finish before I moved to another. I see so many guys that I don't feel pay enough attention to the finish and I think that a great finish is just as important as your skill at turning.

 

[Mark Mandell]

What Finish

Okay, all this being said, here's another question. What is a good alternative to using poly? I have been using that almost entirely because I wanted to get comfortable with one finish before I moved to another. I see so many guys that I don't feel pay enough attention to the finish and I think that a great finish is just as important as your skill at turning.

In my view, it depends on what you want for the particular piece, and, perhaps more importantly, what the piece "wants" for itself.

A high gloss finish sparkles and reflects points and lines of light; it tends to accentuate the design lines of the object.

A low gloss, matte, or flat finish will "hold" the light on the surface, accentuating the mass or volume of the form.

Both may be used on different parts of a piece (like a box with a shiny finial).

I personally tend to shy away from glass-like finishes a) because they are delicate and make the piece seem fragile, and b) because my turnings don't lend themselves to high shines.

That said, dewaxed shellac is a part of every wood finish routine that I use, whether on turnings or flatwork. With the tremendous advances in waterborne finish technology in the past 10 years, most, but not all, of my topcoats are now the acrylic lacquers and polys. I also use tung oil sealers to bring out (pop) grain, but I don't care for the oil varnishes due to their tone and color changes over time. Unfortunately, we are presently experiencing a scarcity (and rising prices) in the types and grades of shellac available, which I hope will be resolved.

Many people tend to look at finishing as a chore, and tend to limit themselves to a single method with which they've become comfortable. In doing so they isolate themselves from the many options and effects that can be used to amplify what they have made. I suggest you gather some scrap wood and spend some time with different finishes to learn what to expect with the different routines, from 1-part to 3-part protocals. Then you'll be in a better position to gauge which you can effectively use on a given piece. I also highly recommend doing some reading on the subject. Excellent books by Jeff Jewitt, Michael Dresdner, Bob Flexner, and others are readily available.

 

[Bill Boehme]

If I want a high gloss finish, I use Deft spray lacquer (I also use a pre-cat lacquer that our club buys in bulk direct from the manufacturer). Otherwise, my finishes range from nothing to wax, oil, lacquer, or shellac. I never use poly on turnings (I do use it on flat work such as furniture and cabinets) because it doesn't lend itself well to leveling and polishing until it is fully cured which would be at least a month or more.

I do not use layers of different kinds of topcoat film finishes except for sometimes using shellac as a base coat. I don't care for the home brew concoctions of different finishes often seen on forums. From what I have seen and experienced, the only things in their favor is that they are fast and easy.

Like Mark M, I have applied lacquer over cured poly without any problems. The key word is cured. I think that the reason that Deft and Flexner don't recommend it is that most people don't understand what fully cured means.

 

[Richard Avram]

Off topic for this thread, but Richard that is a very good looking piece you turned.

Mark

Thanks Mark

 

[Jay Fluegel]

I've only been doing this a short time but the last four pieces I've done with just a few coats of danish oil left to cure for about two or three weeks then using the three wheel buffing system of tripoli, white diamond, and carnuba make for such a spectacular finish without giving any appearance of a film finish I can't imagine using anything else, and is it so simple even I haven't been able screw it up so it must be pretty much fool proof. Of course these are strictly decorative pieces not functional.