Refinishing a bodytop - method

[donnyb]

Hi, Thankyou for reading.
I have a 1970s 12 string Suzuki with a stained spruce (golden teak -ish) and clear lacquered bodytop. I have refinished several guitar tops but only with those requiring re-painting with a solid colour , followed by acrylic or pre-cat lacquer. So entering a new territory with this guitar.

There are no deep dings to the surface.

I want to sand back the top to bare spruce wood, re-stain and re-lacquer, but I have been warned that it may a spruce/ply/spruce sandwich top, not solid spruce, and the top layer of spruce may be very thin. I definitely don't want to hit the ply !

I'm therefore intending to carefully sand just until bare wood emerges.

Could I get some advice on the grit grades to use and also whether I could use an orbital sander , if gentle.
Thank you.

[JonWint]

What's wrong with the original finish?

How will you deal with the stain? May end up blotchy.

Don't remove any wood. Wipe it off with lacquer thinner.

Steam out dings. Scrape flat. 320 or 400 grit for a few passes.

[IMG][/IMG]

[charles Tauber]

Originally Posted by donnyb

I have been warned that it may a spruce/ply/spruce sandwich top, not solid spruce...

The easiest way to determine if the top is solid or laminate is to look at the edge of the sound hole. If it is a solid top, you'll see vertical lines of end grain towards the centreline of the top. If it is a ply, you'll see horizontal lines where the plies are.

In either case, as Jon mentions, you don't really want to remove wood. A solvent or chemical stripper is usually used to remove the finish, if it is a finish that can be removed with a solvent or stripper - some of the modern finishes are impervious and have to be removed mechanically. Some of the modern chemical strippers are more "green", though slower acting.

If you use a solvent or stripper you'll need to ensure you don't get the solvent/stripper on any other parts of the guitar's finish: it will damage them. They can be masked off.

As the solvent works, a paint scraper can be used to scrape the softened finish from the surface of the guitar. If done carefully, little sanding is required. When sanding use a sanding block to keep surfaces flat. Avoid localized sanding to ensure that you don't sand hills and valleys into the surface. Depending upon what the post-stripper/solvent surface looks like, I'd probably start with 180 grit and finish with 220 grit sandpaper. Especially, if it is plied, the sanding should be pretty light.

I would not use an electric sander on it. If the stripper/solvent is ineffective, I'd use cabinet scrapers, though not a tool you are likely to be familiar with.

[donnyb]

Originally Posted by JonWint

What's wrong with the original finish?

How will you deal with the stain? May end up blotchy.

Don't remove any wood. Wipe it off with lacquer thinner.

Steam out dings. Scrape flat. 320 or 400 grit for a few passes.

Originally Posted by JonWint

[IMG][/IMG]

Thanks Jon.

The original finish has a lot of small shallow dings, but also, the bridge had lifted and shaved too low, so I'm currently replacing it.

Worse still, it was also originally set too far towards the rear. But during its removal some spruce splintered, which although repaired now, the repair will be too easily seen with the bridge set forward more.
It is 50 years old, but the back and sides are in good condition, almost unmarked.
So I think its best to redo the top.

I will try the lacquer thinner.

Im fine with ding steaming, and I have multiple scrapers.

The stain blotching . Yes, I know what you mean. It might happen.

I did a violin last year using Zinser spraying shellac and had a great result adding alcohol based stain to it. I had to strip and sand the whole violin as it had been painted ! I have sprayed acrylic clear a lot over many years, but I might go with the spraying shellac again. What do you think ?

[donnyb]

Originally Posted by charles Tauber

The easiest way to determine if the top is solid or laminate is to look at the edge of the sound hole. If it is a solid top, you'll see vertical lines of end grain towards the centreline of the top. If it is a ply, you'll see horizontal lines where the plies are.

In either case, as Jon mentions, you don't really want to remove wood. A solvent or chemical stripper is usually used to remove the finish, if it is a finish that can be removed with a solvent or stripper - some of the modern finishes are impervious and have to be removed mechanically. Some of the modern chemical strippers are more "green", though slower acting.

If you use a solvent or stripper you'll need to ensure you don't get the solvent/stripper on any other parts of the guitar's finish: it will damage them. They can be masked off.

As the solvent works, a paint scraper can be used to scrape the softened finish from the surface of the guitar. If done carefully, little sanding is required. When sanding use a sanding block to keep surfaces flat. Avoid localized sanding to ensure that you don't sand hills and valleys into the surface. Depending upon what the post-stripper/solvent surface looks like, I'd probably start with 180 grit and finish with 220 grit sandpaper. Especially, if it is plied, the sanding should be pretty light.

I would not use an electric sander on it. If the stripper/solvent is ineffective, I'd use cabinet scrapers, though not a tool you are likely to be familiar with.

Thankyou Charles. I have scrapers so I'll favour using them. I wasnt sure how spruce would react with a chemical stripper so good to know I could use it if necessary. I'll try lacquer thinners first as Jon suggested.

[mirwa]

Have you identified if it is a plywood top or not, typical ply layers are .8mm thick or under for each layer, so its very very easy to go through a layer

[donnyb]

Originally Posted by mirwa

Have you identified if it is a plywood top or not, typical ply layers are .8mm thick or under for each layer, so its very very easy to go through a layer

Not 100% sure Mirwa. I will have a good look at it again today , following Charles' advice above re the sound hole end grain. If I cant interpret what I see 100%, I will try taking a photo and post here.

If it is ply, I will try using lacquer thinner to strip the clear lacquer. I can experiment under the original pickguard, which I removed when doing the neck reset . It feels lacquered there, but maybe not.

Funny thing, there was no colour stained top wood under it, and the surface feels clear lacquered, but that might be the remains of pickguard glue I removed . Suzuki must have stained the top , applied the pickguard, and sprayed clear lacquer over the all ? Ever come across that ?

Speaking of pickguard glue removal, after trying all Google suggestions, I found that glue remover strips used for colostomy bag adhesive works great. These impregnated strips come in small sealed packets. It feels like citrus oil and softens the 50year old glue if the strips are layed over the surface for 15 minutes. Easy to remove the glue then with a scraper.

[donnyb]

[QUOTE=charles Tauber;6676918]The easiest way to determine if the top is solid or laminate is to look at the edge of the sound hole. If it is a solid top, you'll see vertical lines of end grain towards the centreline of the top. If it is a ply, you'll see horizontal lines where the plies are.

Hi Charles, Here (I hope) is a photo of the sound hold edge. I think there are vertical grain lines ? Don

[donnyb]

https://i.imgur.com/8zS1BYq.jpg

[donnyb]

Originally Posted by mirwa

Have you identified if it is a plywood top or not, typical ply layers are .8mm thick or under for each layer, so its very very easy to go through a layer

Ive posted a photo of the soundhole.

[charles Tauber]

Originally Posted by donnyb

Hi Charles, Here (I hope) is a photo of the sound hold edge. I think there are vertical grain lines ? Don

The sound hole edge is kind of chewed-up, making it difficult to be certain from the photo, but it looks like it, yes.

If it isn't obvious when viewed in person, I'd start by sanding the edge of the sound hole to expose fresh wood/ply. It should then be obvious.

[donnyb]

https://i.imgur.com/fiIwq3I.jpg

Add an image of pickguard glue removing and the surface of the wood.

[donnyb]

Originally Posted by charles Tauber

The sound hole edge is kind of chewed-up, making it difficult to be certain from the photo, but it looks like it, yes.

Thankyou Charles. I'll still be very careful !

[charles Tauber]

Originally Posted by donnyb

https://i.imgur.com/fiIwq3I.jpg

Add an image of pickguard glue removing and the surface of the wood.

I hazard a guess that the top was not stained, nor was the finish. I suspect the wood and finish have yellowed over time.

[mirwa]

Looks like a laminate to me from the photos, whilst yes a couple of spots almost look like vertical grain, I put that down to more the finish is split and giving the illusion of grain.

Scrape the finish away dont sand it