Official Luthiers Forum!

New to the board. Seems to be alot of good info here. I need help in the polyurethane finish dept.

I guess to start with I can paint cars. I am very familiar with urethane and I like the finish when it is done correctly. I have all the needed equipment for the job and I have painted several guitars and basses with excellent results. However all have been a "solid" color finish. I am building my first bass now. I also have a couple guitars my friend wants me to finish for him. All of these will be a transparent look. While I can handle a "solid" color this deal of finishing so the wood is seen is new to me.

Can someone tell me the steps involved? what I am after is a flame maple top that I can dye just enough to make the figure "pop" and then clear it all. I have an Idea in my head but I don't know how fine to sand it to. Or do I dye it then use grain filler and surface levelers or vice versa.

I have searched on the web but it all leads to how it is done with nitro. All I find on using urethane is for solid colors and just let a body shop do it to save money. Thanks in advance -- I hope what I am asking is a little more clear than mud.

Thanks
Richard

I've never used urethane, but I would think the process for a clear coat is the same as for color, mostly.
As for dying the maple so it will "pop" the grain, a lot of guys will stain with a dark color, then sand back , leaving the stain in the grain. Then follow with clear coats. I'm sure there are a lot of ways to skin that cat, though.
For maple, it is a closed grain wood, so likely will not need a grain filler, although I'm sure there are some who use it anyway.
The biggest difference in shooting clear coats is in the prep. Every imperfection will magnify, so you pretty much need a perfect, pristine surface without imperfections before you begin the finish process. You should be doing this anyway, regardless of whether you're shooing translucent or opaque finish, IMHO.
As to what grit to sand the surface to, I'd sand down to 320.
Hope this helps. There are others here who have much more experience. I'm sure they'll post as well.

_________________
Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

the method of staining the wood and then sanding back works really well in my opinion. nitric acid is even better but it will only give you one color, a sort of golden honey. anyway here is a video that goes through staining on maple, you may not be going after a sunburst finish but most of the principles for getting the color you want will be the same. http://www.finewoodworking.com/SkillsAn ... x?id=30182

_________________
~shad peters

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not sure what look your going for exactly but you could do it like a "candy" paint job on a car. mix a small amount of color into your clear on the first coat, then follow with clear coats as normal. this makes a beautiful finish you can see through with a shade of the desired color.

I am going to the shop today and I'll bring it all home -- I'll try and get up some pics -- I am looking for the dye then sanded back look -- I have several on the warmoth gallery -- I'll see if I put up a link to a pic that has what I am looking for.

Thanks
Richard

Richard is this something like you are wanting only on a guitar?



Automotive clear over House of Kolor tints. Started with black, sanded back to white wood then mixed the teal. These are called Kandy Intensifiers. I am sure most any candy mixing color will work, and with your automotive experience, this will be an easy transition.

One thing to remember though. You are not dealing with a primed surface here and the grain holes need to be filled. On the gunstocks I used to fill them with enough finish, cut it back, wet sand and polish. I discovered after seeing some of my gunstocks a couple years later that figured wood, or open grained wood will have a srinkage over time and the finish will pull back into the grain. You will know it when you see it. Most guitar makers use some sort of grain filler, some epoxy some mineral spirit based. With this type finish, I personally will be using some sort of epoxy to fill the grain.

Now here comes the kicker. I can't tell you when to fill the grain using this kind of process because I haven't done one yet. I can tell you that the solvent based dyes will be better at penetrating that the water based dyes will be, but unless you sand your surface back to raw wood after filling the grain, I bet you will end up with a splotchy finish. This particular gunstock also had tinted clear to build the depth of color, so that is an additional option as well.

I am sure you are aware of intercoat, or jamb clear. If not, you need to find a source as it will allow you to do some of your tinted clear coats with almost no build, and it soaks into the wood pretty good.

Mike

Mike -- yes thats it but I want the natural wood look not a radical color

If can find my camera i'll put up pics of my mess

Radical? Radical? Trust me, that is not radical! Hot pink fading to hot green would be radical!

You need to realize though, that unless you get a little dye, or wash in the grain, with auto clear coat your guitar will look a little bland. If the flame maple top is eastern soft or hardrock, it will be nearly white when you finish it. The west coast will have a little pale tan color to it but neither will have much contrast. Now white is not a bad color if that is what you are going for, but just be sure you know that the auto clear is water clear where most of the guitar finishes have some sort of a slight tint.

I am considering building a guitar top out of Holly, which is nearly pure white. So at least in my opinion, white is a good thing.

If I can help in any way let me know. I have no experience with nitro, but have tons with auto urethanes.

Mike

mike -- ok -- we are gonna do something radical when I get this done -- I have some copper red to green shift HOC pearl that would knock your eys out if used in some sort of sunburst but thats another thread.

I found the camera of course the battery was dead -- I charged it lastnight so when I get home I'll get up a pic. For what it's worth this wood is far from white. I would guess it is not a really good grade of maple but it does have alot of figure. The maple came out of the rafters of a guys barn. He was going to make two muzzle loader stocks out of it. I was told it had been there for many years.

later
Richard

here are a couple of pics










I hope that worked --

Worked fine I Like the looks of that!

_________________
Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

thanks -- I took a test peice of the maple and sanded to 180 then dyed it black -- I sanded back to the original color with 320 -- then I cleared it -- I also sanded the other side of the same stick to 320 and cleared it. the side with the black is the color I want -- it is the same as the the other I just can't believe how much the black makes the figure "POP" and dance as you walk around it. This is the by far the sexyest thing I have ever done with a peice of wood. Pictures just do not do it justice. If my guitar looks as good as my test scraps I might just shead a few tears.

All that is great but I just guessed on how fine to sand and when. The bulk of that body is poplar. I am going to make it dark brown -- I am going to need grain fillers for this unit I am sure of that. I just don't know when in the process to use them. Seems to me like fillers and levelers would mess up your color if used after dye but then what if applied before the dye? -- Will the fillers and levelers take the dye same as wood and disappear? I really need the how to finish a guitar for dummies book -- I know all this is really elementary to you guys but I just can't seem to find what I am looking for.

filippo,

the router bit schorched it some and I have not yet cleaned it up.

I found some help on stew mac but it is for nitro -- should I just follow this kind of schedule and sub the urethane for the nitro?

http://www.stewmac.com/freeinfo/Finishi ... ulose.html