Refinishing 12 string Body Top - update

[donnyb]

Thanks for reading this update to a previous thread of mine.

I decided to scrape the lacquer from the top of the 1970 Suzuki 12 string as it had incurred some minor spruce damage during its un-useable bridge removal and the neck reset.

It took weeks of careful scraping back to the spruce and a light sand all over with 400 grit, and now it is ready for refinishing.

The spruce surface is fairly smooth, i.e. the grains can still just be felt. The top itself has hills and valleys all over due to its age, and as the top is ply construction, it wont be sanded flatter.

I have a lot of experience with spraying acrylic lacquer and also to a lesser extent spray shellac (Zinnser product) and would prefer to use either. I am thinking , due to the undulating surface, to go for a satin finish, and I dont mind if the spruce grain can still be just felt when finished.

However, bearing in mind my finishing preferences, I seek more advice please for what to use for a seal coat and application tips for this and the top coats.
https://i.imgur.com/pidjqix.jpg

[mirwa]

Do you know what thickness the top is at the momment.

Anytime i refinish a top or back i measure its thickness first

Have turned a few jobs down, sometimes they are too thin already

Steve

[runamuck]

Originally Posted by donnyb

I seek more advice please for what to use for a seal coat and application tips for this and the top coats.
https://i.imgur.com/pidjqix.jpg

I'd suggest, no matter what you use as a finish, to seal with Zinsser shellac sealer.

[donnyb]

Originally Posted by mirwa

Do you know what thickness the top is at the momment.

Anytime i refinish a top or back i measure its thickness first

Have turned a few jobs down, sometimes they are too thin already

Steve

I check and reply Mirwa.
Just to clarify where Im at, I have already removed the original lacquer and have done a very light 400grit sand of the now exposed spruce.

[donnyb]

Thanks for the advice. I have refinished a violin with Zinnser spraying shellac. Is this the same product as the sealer ?

[donnyb]

Originally Posted by runamuck

I'd suggest, no matter what you use as a finish, to seal with Zinsser shellac sealer.

This product runamuck ?

https://i.imgur.com/PGPxD12.png

[donnyb]

Photo is too small.
Try this link please.
https://www.dicksmith.com.au/da/buy/...9288577491095/

[donnyb]

Originally Posted by mirwa

Do you know what thickness the top is at the momment.

Anytime i refinish a top or back i measure its thickness first

Have turned a few jobs down, sometimes they are too thin already

Steve

Steve, the top thickness at the soundhole is 2.85mm.

[mirwa]

Thats an okay thickness, 2.6mm and under you got to be careful with.

Shellac it now and paint, or use a rub on varnish

Steve

[redir]

The Zinnser shellac will be a good sealer but it won't give you a satin finish, it will be more gloss. You could rub it out with some coarser rotten stone to go satin but then after years of playing your arm will start to polish it up to a gloss in certain areas. A satin nitro lacquer would be a better option imo.

You might want to dampen a rag with water and go over the top wetting the surface to raise the grain and sand back again to 400.

I'm not sure what you mean bu undulating surface? I cannot see that in the pic. Are you describing something like top belly or are you saying there are undulations between braces or grain lines?

[donnyb]

Originally Posted by redir

The Zinnser shellac will be a good sealer but it won't give you a satin finish, it will be more gloss. You could rub it out with some coarser rotten stone to go satin but then after years of playing your arm will start to polish it up to a gloss in certain areas. A satin nitro lacquer would be a better option imo.

You might want to dampen a rag with water and go over the top wetting the surface to raise the grain and sand back again to 400.

I'm not sure what you mean bu undulating surface? I cannot see that in the pic. Are you describing something like top belly or are you saying there are undulations between braces or grain lines?

Thanks again redir, satin lacquer. Could I use shellac only as the sealer coat/s ?

Im a bit frightened to sand again, counting myself lucky I didnt hit plywood anywhere. I would do what you suggest if it was a solid spruce top.

And, yes undulations between bracings. Small to sizeable areas. Using a 60mm scraper initially with the edge burnished found these areas quickly, so I changed to using craft razor blades with the reinforced top to scrape the rest. It took a long time and a lot of razor blades.......

[redir]

Originally Posted by donnyb

Thanks again redir, satin lacquer. Could I use shellac only as the sealer coat/s ?

Im a bit frightened to sand again, counting myself lucky I didnt hit plywood anywhere. I would do what you suggest if it was a solid spruce top.

And, yes undulations between bracings. Small to sizeable areas. Using a 60mm scraper initially with the edge burnished found these areas quickly, so I changed to using craft razor blades with the reinforced top to scrape the rest. It took a long time and a lot of razor blades.......

Scrapers will do that on spruce tops. Even on a ply spruce I would guess, to some extent. They tend to push down and scrape off the top only to leave ridges. It's difficult to scrape spruce hence why I always sand it. But I would not worry about it.

The purpose of a seal coat is to seal in any stain in the wood and in some cases, like using a sanding sealer, to raise the grain so it can be sanded back. But really, if you want to finish a guitar with nitro for example your first coat, the seal coat, could be nitro too. A lot of wood workers like shellac because it gives a nice color and it's sort of a universal seal coat, it sticks to anything and pretty much anything sticks to it.

[donnyb]

Yes, Im steering towards shellac as I used it on a violin a few years back after stripping all the paint off it (!).

I used the zinnser sprac shellac, but a different seal coat. Cant recall what I used, but runamuck poster (above) suggested using zinnser shellac sealer. Im not sure if the zinnser spray shellac and the zinnser shellac sealer are the same thing. Would you know perchance ?

[donnyb]

The zinnser spray shellac'd violin. Sounds nice too. The product take a long time to dry properly, which can be shelf life related or so I've read.

[redir]

That violin looks great so if I were you I would do what you did there on that violin for this guitar. I do believe the Zinsser spray can shellac is the same as in the can. It's dewaxed shellac with acetone.