The body needs to be sanded to remove imperfections and break the gloss of the previous finish so that the new finish will adhere correctly.
I start with an orbital sander to scuff the finish and break the gloss, and then finish with a hand sanding in graduating grits: 120 to get the imperfections only: 220 to smooth those areas and blend into the surrounding areas: 320 to blend all of that and remove the gloss from the previously finished surface: A scuff pad to break anything else down that I missed. I use that over the entire surface so that all the remaining scratches are of the same type, grit.
At this time all of my holes are drilled and everything is test fitted to make sure of my measurements, fitment. It is easier to correct something now than it will be after you have sprayed your finish coats.
I mentioned that in this build I was looking for a studio guitar to record with. I had concerns: Play-ability, sound, depth, ease of adaptability to various styles: Something in between my other guitars.
You can see the second layer of the ply top on this donor guitar beginning to show. Not the best situation, but I am using the flatter Ovation bridge and although I did radius it I did not want to take that entire radius out of the bridge itself as it would make it a little too thin, and I want a tight fit.
This is the build that I went with, replacing the bridge with the Ovation style pinless bridge, but as I move through this I will continue to provide alternatives to the work I do so that you can arrive at your own level of finish.
PRIMERS AND SEALERS
Depending on the direction you wish to go you will need either a primer or a sealer to seal the base wood before you move on.
Sealers are usually clear, although they can contain color, and primers are usually solid. Both do the same basic job, although there are builders that believe in separating the priming and the sealing steps, I am not one of them. You can, because of that reason, purchase separate sealers and primers: One to do the job of sealing, the other to prepare the surface for stain, color coats, etc.
Once the wood is prepped for a spot repair or a new color spray over the old finish, you can spray one to two coats of sealer over the surface, or brush one to two coats of sealer over the surface. This is to seal the grain of the wood, imperfections, and allow paint/stain coats that are sprayed to adhere uniformly. Without a sealer or primer coat, the paint/stain coats would soak readily into the bare wood surface and only sit on top of the old finish. You would end up with ridges of paint, flat and dull, and it will not only show through your finish but will be impossible to remove without re-stripping the guitar. A few thin coats of Primer-sealer will solve that problem. Sealing the entire surface to make it uniform and paint/stain ready.
With the first method we will finish our prep work, fixing gouges, sanding it all flat, and spray our first coat of sealer over the entire instrument. In this case I have used gray color sealer. I allow this first moderate coat to dry, sand the entire instrument flat, and then spray a thicker second coat over the entire surface again. You can see I am protecting my banding line by sanding back to it.
I will sand this second coat flat with a scuff pad (2000 grit), really I am just going to break the surface shine, not really take any meat away from the material. Take this time to hunt down imperfections and fix them. You can sand an area and add sealer/primer, re-sand it and repeat until you are happy with the results and that surface is as flat as the rest of the instrument. Whether it is colored or clear sealer the goals are the same, to seal the old surface so it is ready for new paint.
For a spot repair you will spray your sealer coats on the sanded/repaired area and flash them (Overlap them) onto the old paint or cleared area. One coat, sand it flat, including sanding the area where you flashed it. If there are no repairs or imperfections spray a slightly heavier coat of sealer flashing a little further into the old surface.
Let this dry and then check it for imperfections. Sand it lightly with 440, or there about, on a block if possible to make sure you stay flat, switching off fingers if you cannot use a block to avoid sanding grooves into the finish. This is a light sanding only. When you are finished the entire surface should still be sealed, but it should also be flat and ready for paint/stain. If it is not, or you had to sand deeper to remove imperfections, simply spray an additional coat to reach that sealed surface you need.
With the surface sealed you can now prime the instrument if it is needed. This will involve possibly spraying a similar color over the entire instrument so that the color coats will match in intensity, or spraying a base coat of a different stain/color to achieve an effect in the finished paint job. For me the primer sealer I used is adequate: I am finished sealing/priming the surface and I am ready to paint it. For a spot repair, use a primer of a similar color or a stain that is close to the color you wish to return to. There are sealer/primers specifically made to do this and they are able to match most repairs on fades, bursts, and most colors.
You are not looking for perfection here, you are only looking for uniformity.
Take a look at the grain. Is it clear? Are repair areas well blended?
In this photo the repair area has been blended into the stock area and the entire area has been hit with a 2000 grit scuff pad and it is ready to spray a stain/color coat. In this situation, and with this particular guitar, there was so much sun damage that I decided to go with a solid color as I knew I would not be able to perfectly match the sun damaged areas.
This guitar is one I stripped, repaired the damaged top and primered it.
A look at color coats on the build. In the image above the repaired top has had the color coats sprayed, but it has not been blended with the darker band at the edge.
Here the color coats and blends have been done…
Here the color coats have been lightly scuffed and sanded back to the white banding, and then clear coated. I used two color coats, and three clear coats. These are lite coats. You don’t want too much paint on the top of an acoustic guitar, it will affect the sound.
Here is the finished product after a light buff. This is crystal, a low luster finish, nearly matte.
You could, however, use a darker stain, blend all the areas together, in effect spraying the entire instrument with a stain or translucent color, clear coating that, and you could preserve the wood grain as opposed to spraying a solid color as I did on the guitar above.
Here I have sprayed my first color coats, a flat gray, and have begun to sand back in places to relic this surface to get the look I want. On your own project, begin with taping the fret board carefully, the sound hole or holes, and then using your readymade paint booth, or a well ventilated room, spray your first color or stain coat.
If I had wanted to retain the wood grain, as with the guitar above, I would have used clear sealers to this point as I did with this electric build. The idea is to take your time to arrive at what you want. As with any project, good prior planning will get you there and enable you to achieve what you want to achieve. This example has had two color coats, or in this case, clear under coats with a slight antique yellow added to the mix to keep the guitar from looking too white. This way it appears somewhat aged.
I could have used any tint in the color coats to arrive here with a red, black, or other color tinting that is embedded in between the coats. I could have also added metal flake to the clear and sprayed that in between the coats. The door is open, limited only by your own imagination.
A body prepared with a blue metallic paint. This is color coated, but not yet clear coated.
A body clear coated with just a small amount of color added to the clear.
If you are doing a spot repair, you will spray your color coats over the damaged area and flash them onto the old surface. Let set 24 hours, tack cloth it (A product made of cheese cloth that is somewhat sticky. It removes particles from the soon to be painted surface, but leaves no residue).
Above is a spot repair, a chip, primed in the first image and then color sprayed and flashed over.
Sand flat, and then respray the color coat, flashing it into the old surface once more. Add a second coat, flashing over the first. It should look like the example, progressing from primer/sealer to color coats applied. Over flash that final color coat with some reducer or thinner (Thinner is used to thin Lacquers, Reducer is used to thin Acrylics) as you clean the gun to help melt the two surfaces to together, Do not worry that this dulls the finish out, the surface will dull anyway as it dries.
At this point we are ready to clear coat our color/stain. The clear coat allows the true beauty of the paint or stain to show through. There are a few types of clear: Matte, Semi and Full gloss. What you use is dependent upon what you want the finished piece to look like. If you are doing a spot repair you want the repair to be the same as the old finish, a complete paint or stain is up to you. Matte will give you a flat paint finish. No luster, and you will have to be careful through the life of the instrument to make sure that the finish is not waxed or polished as that may destroy the matte finish in places. Semi gloss is just that, semi gloss; a low luster in between clear gloss and flat. Semi is what I used on my project, but there are reasons to use the other finishes that are as varied as your builds will be from the next persons builds.
This is the spot repair from above; clear coated and being partially reassembled. It will sit for a few days and then be buffed out. The end result will be a repair that cannot be seen.
The build I am doing will progress with a little more work before I am satisfied with it.
While the other methods are ready for clear coat, my project is not. I want a kicked around look for this guitar so I will add more color coats to it. Grays, whites, dark grays, and I will sand in between those coats exposing under coats in places, and going down to the banding in others. The look I am after is a low maintenance, well used instrument; if you have ever played in bands you know there is a guitar you fall back on.
It may not be the prettiest, but it feels the best in your hands. It’s beat up a little so you don’t have to be too careful when it’s three AM and you are all playing around testing out new stuff. I combined that idea with my love of classic cars and how they look in primer and came up with this.
You can see what I did. It may look horrible to some, or it may look great. The idea is that it should look like what you want it to look like. In this case it looks exactly like what I wanted it to look like, and I was completely ready to clear it, after a little drawing work by a friend.
I scuffed the entire area with a 2000 grit pad, taped the fret board and sprayed my first coat of clear.
I am using a clear lacquer so I followed my manufacturers recommended wait period, and it varies from manufacturer to manufacturer, and since I don’t want to put a time in your head that gets stuck there, I would urge you to be familiar with the paint you are spraying and to read the directions thoroughly so that you know the recommended wait time between coats.
This is an acoustic guitar so my clear coats were thin so as not to affect the sound transfer of the top. Thicker paint will slow the vibration of that top, or tone it down, make it tighter, more material to move as it vibrates. So although you may be tempted to put several progressively thicker coats of clear on, I would urge you not to. If you did your prep work correctly, you won’t need those thick coats to achieve a deep finish that will protect your instrument for its lifetime with no trouble.
Depending on your build, you should now be at the same place and it is time to walk away from the project and let the finish set up well. For most lacquer finishes that is as little as a few days to as many as thirty. For most urethane finishes you can scuff it and buff it the next morning. For most acrylic finishes the recommended time can be as long as sixty days, unless you have used a hardener and then you can safely approach it in as little as 24 hours.
So, as you can see, the time limits really are product dependent. Yet another good reason to check the products you want to use and make sure of the requirements for them. For the same reasons you should not mix products from different manufacturers. Just because it is all Lacquer or all Urethane, that does not mean the results with one manufacture, or the drying times will be the same. You can check the internet, look at pictures of finished items, but that is not usually going to be a good bet. I would suggest visiting guitar shops, looking at instruments that have been finished with the products you want to use in person. That will usually make the difference. And you shouldn’t worry that the people selling the product wouldn’t want you to do that, they should be fine with it. After all, if you buy your supplies from them they have gained a customer. The information you can find on the internet that will be useful is what people that have used that product have to say about it. How it sprayed. What problems they encountered, if any. How it held up. What they learned from spraying it.
My own personal advice is to buy some rattle cans at first. Find something to refinish that isn’t all that important. Learn how to sand, seal, prime, flash your coats, spray your clear coat and then buff it all out. You might spend twenty bucks or so and it will teach you a great deal that will transfer over to spray equipment, or you might decide that you can get by with rattle can jobs. With the quality of some rattle can paints now, between all the steps you do you will not find much of a difference at all: Maybe, only maybe, a little more buffing in the end.
The clear coat is on, and the bridge is test mounted.
We will do the fret job, shape the saddle and nut and put together the rest of build in the next few chapters and finish this project up.
The drawing was done in graphite on top of the sealer coats, and then the two coats of semi clear were sprayed over the top of the whole thing. The bridge is test fitted at this point and all measurements are rechecked before the fret job is done, the bone saddle and nut are shaped and installed, and then final assembly of the guitar is done.