If i start to finish a cabnet in semi-gloss lacquer but i decide that i want it to have a gloss finish can i spray gloss over top of the semi-gloss and have a gloss finish or would i have to strip it back down to the shellac base?

This is going to be on my Westinghouse 16.I have not put any lacquer on it yet.

Nick

You don't need to strip it. You can also buff semi-gloss up to a very high gloss by rubbing the lacquer out and then applying polish.

Peter

Cool.Thanks.

Nick

PETER:
I know you can "buff" a gloss finish down to semi-gloss, but have never heard of buffing semi-gloss up to gloss. Please share your methodology.
BOB

I too had a hard time learning this, BOB. Here's what I think I learned

The "dulling" silicates that are in the mix of a semi or flat lacquer are "suspended" in the coating. I can't think of a better way to describe it in words. The topside will finish off as glossy as glass if you choose to go that route.

The difference between a 'top gloss' and an overall satiny finish as opposed to 'high gloss' all the way thru are very apparent if you were to compare the two side by side. The term 'depth' comes into play and that's why some refinished radios look like they have been dipped with plastic like a Cypress Stump Clock.

I tried some of the Behlen product (a powder) that you can add to degloss your lacquer. Brain lapse...I can't remember the name. (Flattener?) Anyway, you could spray the lacquer which looked as opaque as milk and still put on a glossy surface shine when rubbing out.

The obvious workaround to avoid having a plastic-looking radio, or such issues, is to be stingy with the lacquer. That means good grain-filling is a must. 3-6 light lacquer coats - just enough to flow out, rubbed out to your preference, should be fine. We're not sealing or laminating it. And with that depth it really doesn't matter all that much if you use gloss or semi-gloss.

If you look at the original finish on older radios the lacquer coating is razor thin. Its not a build-up of 1/16" to fill the pores.

Just my observation.

Jack's last couple of paragraphs describe what I do. I usually grain fill at least twice, and the wood is so smooth that it shines without even having a finish on it. I then put a few coats of semi-gloss lacquer on, then rub it out. It comes up to a nice high gloss, but doesn't look real plastic-like.

I use spray can lacquer, and frankly with the Watco stuff, I haven't noticed a huge difference between the gloss and semi-gloss anyway. If the surface is incredibly smooth, both are very shiny (at least to my eye).

Regardless...since everyone uses different materials and different procedures, I should probably ammend my observations above...if you're laying on 12 coats or something similar, I can't say for sure that putting gloss over semi-gloss is going to get your desired result.

This is one that I did as described above, it is semi-gloss lacquer, and then rubbed out and polished.




Peter

I agree with Jack, especially on complete and thorough grain filling. Open grained woods such as mahogany and walnut require dilligent grain filling. If the open pores are truly filled you can actually apply one wet coat of sanding sealer followed by two wet coats of lacquer and the finish will be just fine and measure to be about 2-3 mils in thickness.
Many finishers seem to think that numerous lacquer topcoats are necessary to fill wood pores, however, lacquer does not truly fill wood pores which accentuates the need for thorouh wood grain filling prior to sanding sealer application.
Gloss lacquer is a more durable topcoat than lacquer that has had flattening compound added in suspension. I frequently apply an initial wet coat of gloss followed by a satin or semi-glosss according to the piece I am finishing and the desired end effect. Tom

Beautiful work, Did you use stain or toner for that color? what color is that?

What do you use to "grain fill"? Apply sanding sealer?

Also, how do you "rub out"? use 0000 steel wool

It does fill it if you keep going long enough, but the endless shrinking makes it extremely frustrating. It never ever stops shrinking.

Brett

If you get too many coats of lacquer it can crack.

I am not entirely sure, but I think it probably always cracks, regardless of how many coats you have. It's just a lot more visible when you have an otherwise continuous coat of it. If you just have a thin coat, the cracks are tiny right around the thin spots

Brett

Lacquers, unlike varnish topcoats, actually "fuse" into each other since each subsequent application dissolves the previous one so that irregardless of how many lacquer applications you have there is actually "one coat" so to speak.
Many lacquer manufacturers recommend that you do not "build" lacquer thickness greater than 8 mils due to thermal expansion/contraction and flexibility issues which addresses the tendancy of thicker builds to develop cracks. Tube radio cabinetry may be more prone to this cracking failure since the diffference in temperature (delta T) is quite great due to the ambient heat of the vacuum tubes on the cabinet interior compared to the external cabinet surfaces which are exposed to room temperature. Musical instruments that typically have lacquer finishes such as violins, violas, guitars, pianos, etc. can tolerate a thicker lacquer topcoat due to these thermal issues.
I completely agree with the poster about lacquer applications shrinking during the evaporation/curing process when the solvents go airborne. If the topcoat shrinks 20% then this shrinkage follows the contour of the "open grains" of the wood substrate and this is the reason that lacquer does not fill. 20% of what number equals zero?

Exactly.

While we don't have time machines to go back to the 30's and fix it in the original, adding a plasticizer to the lacquer would prevent most of the worst "crazing" on extremely thick lacquer applications. One of my other pastimes is model airplanes, specifically, C/L Stunt, where the airplanes get judged for appearance in addition to flight. Traditionally, model airplane dope finishes (butyrate dope, a lacquer-type product) have a bad tendency to crack where flexed. The finish become brittle over time, and then any flexing of the (very light) underlying substrate from flight loads, handling, or temperature/humidity variations cracks it. Essentially everyone still using dope and lacquer products - and automotive acrylic lacquer is THE WORST about cracking/crazing - uses some form of plasticizer. Plain old castor oil, in fact, a few drops to half a teaspoon per pint, keeps it a lot softer. Even a little bit would TREMENDOUSLY reduce or eliminate the crazing (like on 50's German radios). Then you can pile it on as thick as you want. Some Stunt plane dope finishes make fine furniture look like it was put on with a roller.

The shrinking is a problem there, too, and even worse because as it shrinks, you have to worry about the underlying structure getting distorted since it's so light. Plasticizer also helps that problem but would not help much on radios or furniture, since its unlikely to shrink enough to crush 1/2" thick hardwood.

Of course a much better solution for airplanes is to use something modern that doesn't have this problem, and also handles the highly solvent fuel getting spilled on it. I wouldn't want to use is for a period application like an old radio, however.

Brett

Plasticizer used in automotive lacquers is good for about 6 months, long enough for flexable parts like bumpers to be remounted on the car. After a while the lacquer will still crack.

Depends what you use as a plasticizer and how much you use. Automotive acrylic lacquer used on bumpers will do as you note. Essentially it's a matter of time before the plasticizing qualities are outpaced by the tendency to get brittle. If you use a lot of plasticizer it won't stick, not enough and it cracks. Acrylic lacquer is just about the worst - I have seen airplanes with it just turn to dust after about 30 years.

Plain old castor oil in dope or furniture lacquer will keep it from the worst of the cracking for at least 20-30 years.

Brett

Nice thread. I have been doing some cabinet work for a couple of years now. I understand the issue of trying to do multiple coats of lacquer with sanding in between. You can never wait long enough for the lacquer to shrink. Please tell me about what products you use for fillers to level the finish prior to spraying. I have yet to see any recommendations. Thanks for your ideas.

Jerry

Why not start your finishes with gloss . You can always buff them out to about any sheen or simply go with semi for the last coat . Jack explained things well .

Hi, everyone refers to grain filler, still waiting to find out what products you use and where to get them. Have yet to find anything at Home Depot but may be looking in the wrong place.

Jerry

Here is one that is mentioned in several threads...http://www.constantines.com/pastewoodfiller.aspx.