Official Luthiers Forum!

Hello everyone,

I am new to the site and a complete newbie to guitar building, I am building my first acoustic guitar following directions from a book although I have come across a stumbling block.

when it comes to cutting the channels for the rosette and eventually the sound hole the book says I must wipe the area on the soundboard with Shellac or Sanding sealer before I do any cutting, I am just wondering if this is a "must do" because I don't have any of the aforementioned items or can you do the cutting out without it?

I intend to cut the rosette channel and sound hole with a small mini router, I also have a big router too but it is powerful and I don't want to risk messing up the soundboard/cutting with that. I have seen people in books and videos not use Shellac or Sealer when cutting the channels out but I'm usually one for doing things by the book. if anyone can advise me on the subject and if its safe to do the cutting without the Shellac/Sealer or if there is an alternative I would be most grateful.

the eventual finish on my guitar is a French polish finish as described in the book I have, so I don't know if any alternative I use will have an effect on that.

I come from the England and shellac/sealer is only available via internet and select places, I have a free weekend this weekend so was hoping to do a lot of work on my guitar, if someone can help I would be most appreciative.

thanks, Jason.

Welcome Jason, really good to have you here. To answer your question, I wouldn't rout for the rosette without first stiffening the fibres with shellac. It isn't so much a matter is sealing but rather stiffening without staining the wood deeply as some other solutions might do, i.e. CA.
But in the larger view of lutherie, in general, is a long pursuit to determine the countless corners one should not cut rather than finding short cuts. It's your guitar, it's your project so you are free to do what you like. I suspect that most of us here would rather forego working on a project in the short term in order to build it correctly and not viewi some fiber tear-out around the rosette every time we pick up the guitar for years to come. You will do well to apply the same philosophy on every aspect of the build.
I am frequently asked, "how long does it take to build a guitar?" Answer, "as long as it takes."

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Doug

Don't let fear or common sense stop you from trying to build something

I have found that if you have a circle cutter (like this one : http://luthiersforum.com/forum/viewtopic.php?f=10117&t=42665 ) you don't need to seal the top with shellac, as the small blade will cut the fiber around the rosette and give a clean perimeter when you take the router to it. The blade needs to be very sharp, as spruce fibers are easy to crush. I still seal around the rosette with shellac, cheap insurance, just in case.

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The top wood is very tender and soft. The shellac toughens the wood so the circle cutter doesn't leave a trail all around the soundhole which you have to sand out. Feel free to ask me how I know this. Lol


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I rout with no shellac, but then apply it after, in and around the channel, so that any black dye from rosette or purfling material doesn't leach into the spruce when the CA hits it. Any blow outs Ive had would not have been prevented with shellac, but it certainly cant hurt as added insurance, for the few seconds it takes to apply. Another tip is to blow the pooled shellac out of the channel with compressed air, so you dont get it too thick, since if your inlay is already a tight fit, it will get too tight with shellac gobs in the channel.

You do realize French polish is shellac right? Since you will need to purchase shellac eventually for your finish, why not use some of it now to protect the top?

I wouldn't use any type of router for a rosette channel without toughening the top first with a coat of shellac. It will also help protect the top throughout the building process. With a new sharp bit and some luck, you might not have a problem routing the wood bare, but why take a chance.

Shellac is your friend, I always keep a can of zinnser dewaxed shellac around for routing sealing channels, etc.

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MK5acoustics.com

My first time in fifteen years to ever hear of a need to apply sealer or shellac PRIOR to routing. After - for preventing ca or glue stains -- yes.
It may be beneficial, probably causes no harm, but isn't required.



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A thin wipe of lacquer or almost any NON - PENETRATING finish will work. Anything that only sits on the surface and will be sanded or scraped off when you level the binding and rosette.

Yes, shellac before routing spruce is a good idea. Zinnser products are readily available in the UK. The aerosol version is very handy for this use. Find a stockist near you at Zinnser site http://www.zinsseruk.com/product/clear-shellac-aerosol/


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wow a bit over whelmed by the responses, kindness and great info from everyone here, many thanks to all.

I will proceed with every ones comment in mind, I'm thinking I will go ahead and purchase some shellac for the rest of my project and future projects and will also purchase some French polish as Cocobolo suggested, I did know that French polish has Shellac in it but I didn't know it consisted mostly of shellac, you learn something new everyday and being a guitar building newbie probably hundreds of things.

I will use shellac/French polish before I route the channels for the rosette etc just as added insurance, better safe than sorry applies a little more here considering I havn't done this before.

thanks again to everyone who replied to my question and I am sure I will return soon needing more advise from experienced luthiers such as yourselves, your knowledge has already helped me greatly.

cheers everyone.

You should probably do some more research on French polish - it is a technique to apply shellac, not a type of finish. There probably are cans of finish labeled "French polish" out there in stores but they'd actually be a bit misleading because as I said, it is a technique, not an actual 'product'.

As to the routing, I tend to use shellac when routing for rosettes but it's not essential as the others have commented. I think it does eliminate a bit of splintering but, using a downcut bit eliminates it even bettererely.

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I use a Dremel with a down shear bit for rosettes. I've never sealed with shellac prior to routing, though I could see the advantage I doing so.

I do however, seal the routed channels before installing the rosette.

Here's what I do...

Route, seal, install rosette, flood with CA.

I think my circle cutter is just crummy. It made a line all around my rosette which I had to sand out. After that I applied two coats of shellac. I felt like I was closing the barn door after the horse had gotten out. I will always shellac first. Doesn't take much to remove it before finishing. It is a very tough surface. Just my 2 centavos


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Hi Jason,
As has been said "French Polish" is just a technique for applying shellac. When you buy shellac, try to find it in the dry flake form and dissolve it in denatured alcohol to make your F.P. Freshly made shellac generally dries faster than "off the shelf" stuff.

I use the shellac first and have not had a problem with rosettes or binding/purfling channels. It helps to wipe on a coat to the entire top as also it helps keep it clean. At first I was told that the shellac will make the tape for the binding/purfling easy and clean to remove but found the hard way the you have to heat the tape with, say, a hair dryer or you will pull up fibers, even with the shellac.

If you cut a few corners on your first guitar, you will learn where you can cut corners.

Ed

Shellac is a good idea but not a necessity.............more important in my mind is that bits be super sharp.
Tom

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A person who has never made a mistake has never made anything!!!

Hi I am in Nailsea just south of Bristol. I know lots of places local and not so local so if you want to drop in and see me some time I can help get you started. Also if you want to meet up to swap ideas etc or need any help just PM me. I am pretty new at this "looferie" business too but do have lots of woodworking experience.



Cheers, Bob

I never use shellac on rosettes. I always use 3 coats of lacquer rubbed into the grain with a paper towel. I let it dry overnight and then begin routing. The insurance costs next to nothing...

+1 for downcut spiral bits. They're more expensive but the results are well worth it.

A drill press and a fly cutter will also cut a very clean slot. If you get a spare bit and custom grind it, they will cut a nice flat bottom slot.

It should be noted that they are potentially dangerous if used incautiously.

There's also the fancy drill press rosette cutter LMI sells. If I was running a small production shop - or in fact were anything other than a hobbyist - that would be my rosette cutter of choice.

Egg Whites.

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."