Couple of Shellac Questions

[LHawes]

First, I will put a coat or 2 of shellac on the tops during construction for protection and was curious if others do the same and do you leave it on before spraying with nitro (in this case) or sand back back to bare wood before finishing?

Second, do any of you all put a thin layer of shellac on the interiors of your guitars? Or would one expect a visit from the tone police with that layer of shellac on the interior?

Thanks

[srick]

Yes and yes. Even if the coats of shellac before spraying are thin enough (1 lb cut), a light sanding is a good idea just to smooth out any irregularities. Shellac sticks to most anything and most anything sticks to shellac. It’s a wonderful substance and so easy to use.

Have you filled the grain yet? IMO, the smoother the surface is prior to lacquer, the smoother your lacquer finish will be and the thinner that your finish will be.

As far as shellacking the interior, it makes sense to me, and I have done it. But no one to my knowledge has really measured any appreciable difference. I do it in hopes of slowing the rate of moisture exchange between the wood and atmosphere. It also makes the interior of the guitar smell very sweet, so why not?

Make your guitar anyway you want to. There are no grades on this exam, except how you wish to grade yourself.

[Bowie]

Many do both. It's a great sealer/ground on the top.
On the interior, the benefit is debatable. A negative you must weigh is... well, the weight itself. Is that additional weight of setting any advantages you might be getting? And, if this is something you plan to sell, will buyers be put off by a non-traditional looking interior.

There's no right or wrong so it's totally a personal choice. I don't think you'll make or break with either one.

[Alan Carruth]

Future repair people will appreciate it if you don't finish the inside. It may slow moisture exchange a little, but it also interferes with gluing.

[nikpearson]

It can make future repairs a little trickier. Shellac will adhere to nearly everything but glues do not usually adhere well to it.

It should slow down moisture being absorbed or lost from the wood somewhat which can be a good or bad thing depending on whether your instrument is dry, wet, or just right.

I love the look and feel of a well applied French-polished shellac but a light coating or two on the interior isn’t the same thing at all. I tried this once on the interior of a classical guitar and ended up removing it becaus it looked patchy rather than even.

Good luck with your finishing.

[redir]

Shellac is commonly used as a sealer under nitro. Just make sure it is a thin coat of shellac and that it is dewaxed shellac. Use a French Polish mouse and just rub one thin coat on. Reason being is that shellac is a bit softer than Nitro and the adage is - well that escapes me now but- a hard finsih over a soft one can cause crazing. But again shellac under Nitro is very common.

When I spray Nitro I don't seal it with anything except a 50/50 Nitro/Reducer solution. So it's technically still a nitro sealer but it goes on thin.

[Quickstep192]

On one of my banjo builds, I shot a couple of thin coats of shellac with the intention of topcoating it with nitro, but l liked the look of the shellac so much, I just kept going.

It has held up completely well and it look terrific. It’s much more vintage looking (to me)

[nikpearson]

Originally Posted by Quickstep192

On one of my banjo builds, I shot a couple of thin coats of shellac with the intention of topcoating it with nitro, but l liked the look of the shellac so much, I just kept going.

It has held up completely well and it look terrific. It’s much more vintage looking (to me)

I’ve experimented with both high gloss and satin shellac finishes. When done well it looks incredible and given enough time becomes very hard. While not as durable as nitrocellulose or more modern finishes, much of that is down to the thinness of French-polished shellac. I’d guess that this is typically only 10 or maybe 20 thousandths of an inch. Top-end classical instruments are usually finished with shellac and I’m seeing an increasing number of sole-luthier steel-string guitars employing shellac.

Other big advantages are the relative easy of repair and no requirement for specialist spray equipment and extraction.

Can you tell I’m a fan?

[Fathand]

Originally Posted by LHawes

First, I will put a coat or 2 of shellac on the tops during construction for protection and was curious if others do the same and do you leave it on before spraying with nitro (in this case) or sand back back to bare wood before finishing?

Second, do any of you all put a thin layer of shellac on the interiors of your guitars? Or would one expect a visit from the tone police with that layer of shellac on the interior?

Thanks

I often put a thin shellac coat on while building. Dont forget to mask the bridge area so you glue it to bare wood.

My understanding is Selmer Macaferri guitars (Django guitars) are sealed on the inside. If you seal after building, there will be no shellac under the braces to interfere with re-gluing at a future date.

[redir]

Originally Posted by nikpearson

I’ve experimented with both high gloss and satin shellac finishes. When done well it looks incredible and given enough time becomes very hard. While not as durable as nitrocellulose or more modern finishes, much of that is down to the thinness of French-polished shellac. I’d guess that this is typically only 10 or maybe 20 thousandths of an inch. Top-end classical instruments are usually finished with shellac and I’m seeing an increasing number of sole-luthier steel-string guitars employing shellac.

Other big advantages are the relative easy of repair and no requirement for specialist spray equipment and extraction.

Can you tell I’m a fan?

How do you do satin shellac?

I just ordered some Mohawk Flattening Paste after talking with Jeff Jewitt. Is that what you are using?

https://www.mohawk-finishing.com/pro...latting-paste/

[SColumbusSt]

Originally Posted by redir

How do you do satin shellac?

I just ordered some Mohawk Flattening Paste after talking with Jeff Jewitt. Is that what you are using?

https://www.mohawk-finishing.com/pro...latting-paste/

I've done one satin shellac finish. Two week, every other day French polished as normal and then once the finish cured I lightly buffed the top with a green 3M pad to knock off the shine.

[Alan Carruth]

A good French polish job is .002" thick, or a bit less. Most brushed varnishes are a bit thicker, although some will end up at .003"-.005" or so. Typically a spray finish will be .005" or thicker, and in some cases much thicker. I have a cut off piece of an Ovation top that has .04" of hard water-cure epoxy for a finish, sprayed on in one coat, or so I'm told.

The best test of finishes I'm aware of, Schlekie's paper in the old Catgut Acoustical Society 'Journal' pegged shellac as about 1/3 less hard than nitrocellulose lacquer. Compared with many oil-resin varnishes that's pretty hard, although some of the modern ones seem to approach nitro in hardness. Shellac is also tougher than nitro; more likely to dent than chip at a given thickness. At .002" thick no finish is doing much as an 'armor'. You can, of course, lay on shellac as thick as you like.

[nikpearson]

Originally Posted by redir

How do you do satin shellac?

I just ordered some Mohawk Flattening Paste after talking with Jeff Jewitt. Is that what you are using?

https://www.mohawk-finishing.com/pro...latting-paste/

I’ve used both to produce a satin finish on shellac. Grey Scotch-Brite pads knock back shellac to a soft sheen; white pads are finer leaving a little more sheen. Liberon 0000 wire wool produces a similar finish to the grey pads but tends to clog more quickly. On the top and back I ‘ll use a cardboard straightedge to keep the scratch pattern parallel; sides and neck are done freehand but still trying to keep an even pattern.

Satin shellac was employed out of necessity on a double top classical guitar I made. There were scratches in the soft cedar soundboard outer skin that couldn’t be sanded out without going through to the Nomex inner core. Gloss shellac made these really stand out so I experimented with the above. The final finish looks and feels similar to the hand-rubbed nitro finish Lowden create.

[redir]

Wouldn't the rubbing of cloths, sleeves, leg rests, and so on polish out the guitar if it was simply satin-ized with steel wool though?

[runamuck]

Originally Posted by redir

Wouldn't the rubbing of cloths, sleeves, leg rests, and so on polish out the guitar if it was simply satin-ized with steel wool though?

Yeah, that's been my experience.

I've also seen that happen with satin finishes where the sheen increases because of what you've mentioned.