May Guitar of the Month

May 12, 2017

This month were are featuring a very talented luthier, Kelly McDonald, from McDonald Guitars! Read along as he shares how he achieves his beautiful guitar finishes.

My latest build, shout outs and relationships:

The guitar I recently finished is a mahogany body with a Black Walnut and Paduk top that my buddy Rob from Robs Wild Wood made for me in Texas. He has been making knife scales and pistol grips for years and wanted to get in to making guitar tops, so he sent me a top set to build a guitar out of. The reason I feel it's so important to talk about the body wood and top wood is the grain and filling that grain is of key importance. The fingerboard is Black Walnut and came from my buddy Nate Stott Wood. I'd like to give these guys a shout out because without them, this build wouldn't be. I can tell you, in this business, relationships and networking are of the utmost importance. Which is why I choose to do business with Mohawk Consumer Products. Not only do they have thebest, most user-friendly products, the staff there is great. Have a question, give them a call and talk to a real person who can help get your question answered. That really matters to me and it's obvious that it matters to Mohawk as well.

About Me and My Gear:

I have been a professional musician for 25-odd years and only been building guitars for a couple of years now. I started building guitars because I would go out on tour, come home flush with cash and blow it all on guitars. I have worked wood all of my life, and decided... "can't be that hard to build them". I built myself one guitar and it kind of took off from there. My mission is to be able to build amazing, custom guitars that "guys like me can afford". Most of my builds are under $2,500. I do all of the woodworking portion in my home workshop by hand, no CNC machines here. I have learned as I have gone and started with rattle cans and moved up to a spray gun from there. It wasn't quick or easy to learn by trial and error. I hope this will help people who are trying this for the first time. I do not claim to be an expert in the field of finishing guitars but these processes work great for me and I hope for you too. I do have a spray booth at my disposal a few towns away and that is where I do all of my spraying. I wear a high quality 3M respirator as well as nitrile gloves when I spray. I started out with a Harbor Freight Gun and went to a Husky gun from Home Depot. I now have better guns, but I still really like to use my Husky one for some reason. It's just a great gun, especially for the money. You do not need to start with a DeVilbiss or Iwata gun, but please (for your own sanity) skip the Harbor Freight guns and go straight to the Husky gun, as it is a far superior gun in every way. All I have ever used is HVLP gravity feed guns and could not be more happy. I have sprayed many different brands of lacquer as well as types including waterborne which. The Behlen Nitro is the easiest and best of all I have tried, plain and simple.

Getting to it:

With the guitar sanded to 220 grit and clean and free of sanding dust.
Pre Stain: If you are going to do a rub on stain or burst using either a stain from a big box store, Dyes or anything of the sort you will need to have it done at minimum 24 hours before you start to spray any finish on it.. A few days is better yet. I do most of my bursts and stains this way and I won't get into how that is done because it is a whole other conversation.

Prep:

Sand body to 220 grit, blow off with a compressor and wipe down with a tack cloth. You can get a tack cloth at any home improvement store. I also tend to only handle the guitar with Nitrile or latex gloves at this point. Gotta keep the hand oils off the guitar.

To start with: on all guitars it needs what's called a "washcoat" which is lacquer thinned out 40-50% with reducer. Brand: Behlen Stringed Instrument Lacquer and Behlen Lacquer Reducer. I can tell you from experience that if you're using the Behlen Nitro, you NEEDto use the Behlen reducer because the big box store stuff will yellow the nitro. You can and should use the cut rate local hardware store lacquer thinner to clean your gun though.

Step 1:

(2) washcoats sprayed 2 hours apart 50% Behlen Stringed Instrument Lacquer and 50% Behlen Lacquer Reducer

Step 2:

Grain filler. Woods that I know of that will need grain filler are: Paduk, Ash, Mahogany, Koa and Walnut. I currently use the Timbermate Brand grain filler for no other reason than I have been using it for years on cabinetry. This is water based so it is extremely easy to thin out and work into the grain. I mix it with WARM water and mix until it is the consistency of guacamole. It is completely fine to have it thicker or thinner. It doesn't seem like it will fill the grain when it is thinner, but it will. As I said in my intro, the grain in Mahogany and Paduk is pretty severe so if you're using these types of wood, you will need to grain fill them. You need to be prepared to do at very least 2 coats of grain filler.

How to apply:

Once it is mixed to the desired consistency, go ahead and wipe it on using a paint brush, a Behlen Grain Filler Spreader, Bondo Spreader or even an old tee shirt. I use a paint brush and the Behlen spreader. You're going to brush it onto the guitar going across the grain... wait a few minutes and once the filler starts to dry (the color will start to lighten up) holding the spreader at a 45 degree angle, wipe of the excess with the grain. Wait 24 hours and sand it smooth. If you get it in the light, and get it to glare, you will be able to see if you filled it enough. I can almost guarantee you will need at least 2 coats. The guitar I am discussing took 3 coats to fill the grain. While I'm on it, you can pretty much use any color you want to for grain filler. One of the most common things is to use the opposite color as grain filler, but on this guitar (medium brown, dark brown and orange colored wood) I went with an ebony colored grain filler. I wanted to make absolute certain that I would not take away from the amazing top my buddy Rob made me. Once grain filler is dry and grain is filled, sand to 320 grit.

*Wait at least 24 hours (longer is better) after using water based grain filler before the next step*

Step 3:

Sealer coats:

I use the Behlen Vinyl Sealer minimum 4 coats (body only, not the neck). You can use the lacquer for this but it doesn't sand nearly as easily as sealer does and it will clog up your sand paper unlike sealer. Depending on the size of your needle in your gun, you may have to thin the sealer as well. One of my guns has a .08 needle and I have to thin it down up to 50% depending on how cold it is in my buddies spray booth. My 1.4 tip gun, I thin it down 10% on average. You will need to figure out your gun which is a whole other conversation but there are plenty of videos on youtube that can help you there.

Spraying the sealer: As I said: Minimum of 4 coats, sprayed 2 hours apart and no more than 3 coats per day.

Once you have your 4 coats laid down wait 24 hours and then sand back using a block and some stikit sandpaper. I have a 10" long block and I go sideways with it. The main goal here is to get the finish perfectly flat. Best to do it now and not chase it from coat to coat. (trust me)

I finish this step with anything from 320 grit on up to 600 grit. My local Ace hardware sells these little foam sanding blocks in various grits and I go with what they call 400 which is closer to 600. All you're basically doing here is trying to make sure you don't have scratches too deep or widebutyou do need to have some smaller scratches there for the next coats to really lock in there. Blow off with compressor, and then tack cloth it.

Step 4:

Color:

If you are going to spray color such as a burst now is the time to do so. I did not add color on this particular guitar but have in the past. Get yourself a jelly jar and add some Behlen Stringed Instrument Lacquer to it, mix in some dye... I use the Transtint Dyes because I can get them locally. This one is going to be an eyeball type of deal depending on how light or dark you want the color. Basically on a traditional 2 color sunburst you have amber and black or tobacco brown. The way I do it is to (using my airbrush) do the black around the edges and get that how I want it and then shoot the whole thing with the amber and my regular hvlp gun. I spray over the black and everything because you will never see the amber on the black. Do no more than 3 color coats (each color). Wait 24 hours, sand it back and get it to 600 minimum, blow it off, tack cloth it and move on to clear coats!

Step 5:

Finish Coats:

You're going to need to get a minimum of 8 coats on. If it is your first time spraying or doing this, you're going to need to make sure you get at least 10 coats... 12 would be better. Remember, too few coats and you will sand through later, too many coats, you will get "checking" or cracking. Do no more than 3 coats per day no matter the temp. You can do what's called a tack coat, which is a light coat and come back an hour later and flood it. I have done this but it's not great for beginners. It's far too easy to get sags or runs if you don't have any experience in using a spray gun. I shoot 3 "regular" coats anywhere from 1-2 hours apart. Usually, I set my phone timer to 1:40. With nitro, you do not need to sand between coats unless you get past 24 hours, but I would imagine that it would still be fine to do so without sanding it back, being that nitro will do what's called "burn in" where it melts into the coat underneath. This is what makes nitro forgiving to work with. If you have weird spots that look like bubbles, or craters you can put a couple drops of Behlen Fisheye Flowout in your lacquer on your next coat. I can't stress to you enough, if you are buying your first quarts of lacquer to give this a try... buy it with your first quart. Also, if you are in a high heat, high humidity area you can use some Behlen Lacquer Retarder. This will help slow down the cure time to let it cure more fully without trapping a bunch of moisture in it. Anyhow, after you get to your final coat, wait 10 days... ideally, you will have the guitar body hanging to let it cure and off gas. After 10 days, you can start wet sanding.

Step 6:

Wet sanding:

Depending on how good of a job you did with your spraying you can start with 1000 grit. If your finish is really rough, you can start with a heavier grit but remember, you can very easily sand through. I have gotten good at spraying over the years and can start at 1500 grit so stick with it and your life will get easier. Sanding mixture: I use tap water and Murphy's soap. I have heard different amounts of soap from different people but I use 1% give or take. You can use a couple of drops and it will be just fine. I like to make up the mixture the night before and put my sandpaper in it and let it soak overnight, that way it is soft and pliable the next morning when I am ready to sand. When you do start wet sanding, you will need a good light, or the sunshine. Sand in a small area and wipe, then look at it in the light at all angles. Keep on sanding until you get all the shiny spots out. Once you get that done, move up to the next grit.... all the way up to 2500. As I said before, you are making your sanding scratches smaller and smaller as you move up in grits.

Step 7:

Buffing:

I do not have one of those amazingly awesome buffing machines. What I do have, is an 18V Makita drill and a 3" Velcro backing pad I ordered off Amazon. You can get the whole set for around $12 if I remember right. The pads that come with it are basically not great, and they don't tell you what pad is hard, soft or anything. It's really tough to figure it out. I use the Meguiars pads for their DA buffer. I do not have the buffer, just the pads. They Velcro right on to the backing pad I got with my set from amazon. They have maroon which is hard, yellow which is softer and black which is the softest for waxes. All of the compounds I use are Meguiars and you can get them at Auto Zone or pretty much anywhere. If you get it to 2500 grit with your wet sanding like I do, you can go ahead and start with "Medium Cut Cleaner" on the maroon pad. I put the compound directly onto the pad and give it a light squirt of water with a spray bottle. Start off slow otherwise you will end up wearing a lot of compound. As soon as you feel like you won't fling it everywhere, turn up the speed on your drill and keep moving,do not let it sit in one place. Grab a microfiber towel, and wipe off the compound. Get another new pad, then I go to machine glaze and repeat the process. You need to use different pads and microfiber towels for each compound you use. (trust me) lol. After the machine glaze, I let the guitar sit for a couple more days and then wax it. You can assemble at this point and then wax around your controls and so on but since mine are for paying customers, they get wax everywhere. I personally use the hi tech yellow wax but any wax will work. You need to wash out your compound and buffing pads as soon as you are done using them. Warm water.