Color Matching an Existing Finish

Sometimes you encounter situations that require you to color match a finish.  In this case it is with a bass guitar that had its peg head shape altered and the client wanted me to match the finish as close as possible to the rest of the neck.As you can see, the fret board (as is the rest of the neck) is a dark amber color, much darker than the rock maple.

First, I sand to 220 grit to get rid of any scratches and prep the surface.  In fact I do this even if there aren’t any scratches to make sure there is nothing contaminating the wood.  Then I apply my sealer, in this case shellac.  You can also use vinyl sealer, epoxy and sanding sealer but in this case it was handy.  When it comes to shellac I try to always use flakes dissolved in alcohol with a date on it to make sure it’s fresh.  I usually use a 3 lb cut as a sealer.  This refers to 3 lbs of shellac dissolved in 1 gallon of alcohol.  It lasts for about 6 months so I don’t mix more than I can use in that time period.  It should be dry to the touch in minutes, and if it doesn’t it’s old and should be thrown out. The pre-made shellac in hardware stores contain too many additives such as plasticizers to maintain shelf life.  An interesting thing about shellac is that it’s considered a food product by the FDA and it’s what coats M&M’s.

I don’t like to stain bare wood for two reasons:  One it looks blotchy.  The soft parts of the maple will take more stain than the hard parts.  Two, if I screw up the color, I can take it off easier.  Here’s what it looks like with the shellac applied.

I mask off what I don’t want finished and mix my color.  I don’t normally shoot lacquer but in very small amounts I can get away with it (I’m allergic to the stuff).  In this case I’ll be using TransTint dyes sold by Stew-Mac, amber, red mahogany and medium brown.

Most of the color matching comes from practice.  I’ve done a lot of these so I use my experience to make a guess as to the colors and ratios.  In about 4 oz of lacquer I put 6 drops of amber, 1 drop of red mahogany and 1 drop of medium brown.  It’s very important to make a record of this and keep it in a journal.  This way you will be able to correct the formula if it isn’t right and repeat it if it is.  I test the color on a piece of paper and in this case it was pretty close so I went ahead and shot the peg head.  I do very light layers until I get the desired shade.
As you can see, it’s a pretty close match.

Next week, the finish coats.

Resetting a Neck on a Bozo Podnuavac Part 2

Now that we have the neck off, and I’ve let it dry for at least a week, we can proceed to the reset.

This guitar will have a fret job as well so all the frets were pulled.The first step in the reset is to determine how much of the heel needs to be removed.  As I stated in the previous post the current neck angle left the straight edge about 1/8″ above the top or about 1/4″ too shallow.   Since the heel is about 4″ and the distance from the nut to the saddle is about 25 1/2″ it takes a fraction of amount taken off at the heel to make the 1/4″ needed to correct the angle.  My usual formula (not scientific by any standard) is to take about an 1/8th of the amount off the heel.  So in this case, I would take off a 1/32″ from the heel or an 1/8th of the 1/4″.  Some people use a file to do this but I prefer a very sharp chisel.  I cut to the line on a bevel, then back cut on a slight angle so that shoulders of the neck “bite” into the body. I may repeat this several times, until I get the angle right.  Make sure you take the same amount of material off both sides of the heel to maintain the correct trajectory to the bridge.

This gets me into the ball park, but I use another method to get the final fit.  For this step I use 100 or 120 grit self adhesive sandpaper with the backing left on.  I put the neck on the body and put the sandpaper between them, slick side toward body.This does the final fitting.  I’ve run across several bodies that are not completely flat, so this works very well for this.  Make sure when you are doing this, you do not pull the sandpaper up because you will take too much off the heel.  Again, care should be taken to ensure both sides are even.  When you are satisfied with the fit you must now adjust the dovetail geometry.

I you have taken more than an 1/8″ off the heel you will first need to take off material off the back of the dovetail to clear the back of the head block.  Once this is done you can now make the shim for the re-fit.In taking wood from the bottom of the heel you will have a lose fit because the dovetail is now smaller at the bottom.  The top should be relatively tight because no material should have been removed (in fact, if wood is taken away form the top of the dovetail, it will effect the intonation because the neck will be closer to the bridge).  I make two wedges, one for each side of the dovetail.  Using .032″ thick veneer 5/8″ wide and almost the length of the dovetail I taper the thickness from the full .032″ to nothing.  A trick for getting this done is to use a piece of double stick tape on one side of the shim so that I can secure it to my fingers while sanding. Carbon paper or lamp black used in between the neck and head block is a good way to test the fit.   I do this until I”m satisfied with the joint.  I have to say that the original dovetail was a very fine fit, a testament to Mr. Podnuavac’s work.

I then glue the neck back on using the same type of glue as the original.  In this case hide glue was used.  NEVER use epoxy, polyurathane or any other glue that can’t be reversed!!!   I touch up any finish issues, such as chipped lacquer around the body or neck.

The 15th fret will have to be replaced, making sure it is in line with the others and doesn’t cause any buzzing (in this case a re-fret was needed).  Finally a new saddle will have to be constructed.

Even if you never do this on your own guitar it will give you some understanding of why this kind of repair costs so much money.

Resetting a Neck on a Bozo Podnuavac Part 1

This is a pretty common but more advanced repair.  Steel string “flat top” guitars have over two hundred lbs. of force from the strings trying to collapse the neck into the body.  Unlike classical guitars where the neck is part of the head block (they have much lower tension), steel strings were made with a neck separate from the body so that they can be disassembled.  Most of the older instruments use a dovetail, either tapered or straight, to attach the neck to the body.  A lot of modern luthiers use bolts to anchor the neck.  There has been a lot debate about what’s better, but as someone who has built over 50 instruments, half bolt, half dovetail, I can’t tell the difference in tone.

If you lay a straight edge along the fret board on a guitar with a proper neck set, the straight edge will just come to the top of the bridge.  A saddle that is too short or too tall will affect the tone and playability.  A general rule is about 3/8″ above the top at the bridge position.

A common method in the past was to shave the bridge (not a good idea) or to “slip the block.”  This is when the back was heated and pressure put on the neck to “slip” the head block, moving the neck angle. When the back cooled the glue would harden.  The problem is that the back was exposed and needed to be trimmed and rebound.

In this example, I’ll be resetting a neck on a guitar by Bozo Podnuavac (pronounced Bo-zho).  He gained fame in the 70’s for his flamboyant 6 and 12 string guitars played by people like Leo Kottke. 

This guitar had been pretty mistreated.  The head stock was broken and poorly repaired.  Numerous cracks have been haphazardly repaired and pressure from the neck had cracked the top on both sides of the fret board and moved the head block toward the body.

A straight edge determined that the neck angle left the height at the bridge about 1/4″ below what it should have been.

The first thing I need to do is separate the fret board from the body. This is done by heating the fret board and carefully working a thinned putty knife under the board.  I’m very careful about this and don’t force the knife.  When the glue is soft it will slide under the board fairly easily.  LMI and a few other companies make a silicone heating blanket just for this purpose.  Stew-Mac also makes a massive iron with space milled for the frets just for this purpose.  In this case I’ll be using the blanket

If the neck joins the body at the 14th fret I pull the 15th fret to make way for two holes I drill into the slot.  In a typical dovetail the male portion of the neck is about 5/8″ long and the corresponding female joint in the body is 3/4″ deep.  This leaves a gap in the head block and the 15th fret is about 5/8″.

Two tools that I think are essential are from Stew-Mac.  One is the guitar neck removal jig and the other is the neck steamer needle and hose.

The other necessity is a cheap coffee maker capable of making steam.  I set up the removal jig as in the picture and turn the cappuccino on steam and wait for the unit to heat the water.  As an aside always use distilled water or you will have a great deal of mineral buildup.  I put a slight amount of pressure on the bottom screw of the jig, just enough to ensure the jig is not moving.  The steam works very rapidly to soften both hide and yellow glues.  I usually only have to wait 5 or 6 minutes for the joint to loosen.  I keep putting slightly more pressure on the bottom screw until the joint separates.   I also elevate the bottom of the guitar so that all the water from the cooled steam stays relatively contained.  Tapered dovetails remove the easiest but in some instruments the dovetail is straight and they require constant pressure because of the friction.

Sometimes, however the mojo doesn’t work, and this was such a case.  After waiting over 10 min. the joint had not budged!  I was afraid that the joint may be epoxy.  Mr. Podnuavac is still building guitars at 82 so I called him in his current shop in Florida and he did indeed confirm that the joint was a dovetail and should come off.

Take two:  This time I put a little more pressure on the screw and after 10 more minutes it did break loose.  If you look at the truss rod you can see a grey bar on either side of the truss rod housing.  This appears to be epoxy that goes through the head block and under the top. This is what I think was causing the hangup.

Next week.  Refitting and re-gluing the neck.

Gibson Style O Artist part 4: Finish, Setup and Trouble Shooting

It finally looked like a guitar again.  I sealed the body with Tap marine epoxy.  I did this because the body was pretty dried out and I thought the epoxy would better integrate the surface.  It’s also what I do on my own instruments. 

After it dried a toner coat of  finish using yellow metal acid dye was applied over the entire instrument.  We had agreed to go with amber to dark cherry for the sunburst and dark cherry for the rest of the instrument.  I wanted to go quite dark on the edges and sides to try and hide some of the severe damage to those areas.  One note, I had put in the pearl dot at the center of the scroll, as per all the pictures I had seen, and when I sent the pictures of this guitar for approval on the finish color, I had forgotten about the conversation we had about omitting the dot. It was a quick fix, but also a reminder to write everything down.

After scraping the bindings I sprayed 6 coats of KTM-9 (before anyone howls, I’m severely allergic to lacquer and don’t have that much experience with varnish) sanding every two coats.  I tinted the finish with a slight amber color to tone down the new ivoroid, and to blend it in with the existing pieces. Although I’m not sure that was necessary because only the heel cap, soundhole surround and the tip of the Florentine cutaway survived.  I also saved small jars of the colors so if I went through the burst I would have a match to the previous colors.  It probably would have been smart to document the ratios, but if I were smart I wouldn’t be building guitars for a living.

On the Gibson HG I repaired I didn’t finish sand the final coat of finish, just buffed it out to a gloss leaving all the imperfections.  It is an 85 year old guitar and it was decided that it should look a little lived in.

The tailpiece had been broken and Jim had that fixed but the plating had been compromised, so he found a place to get it re-plated.  The holes for the bridge pins were way oversized by wear, so I used some celluloid pickguard material to line the holes of the celluloid tailpiece, and cement them with acetone. The hardware was installed next, followed by a level crown and polish of the frets and cutting the nut slots. It was interesting to me to see that in most of the pictures of Artist O’s the three in line machines were installed upside down, the knobs being below the posts.  Since the back of the peghead was now free of any holes I thought it best to put the Waverly’s with the name up as on a modern guitar.  I was concerned that they might not hold up as well upside down since they weren’t designed to be used that way.

I only had light gauge strings on hand and even though I thought they’d be a little weak in tone, I was anxious to hear how the guitar sounded.   After bringing the guitar to pitch I was thrilled with the sound.  It was much more alive than I had thought it might be, very rich, even with light gauge strings.  Unfortunately, it became obvious I was not finished with the job. After only five minutes the top on the treble side had started to cave in.  A depression was forming around the foot of the bridge and I immediately detuned the guitar before I had a catastrophic failure.  Apparently, my predecessor had been a little too overzealous in his working of the top and it was way too thin.   I didn’t think to check the top’s thickness before I installed it on the body.  This is another mistake I will not make again.  I thought the best way to handle this was to make a “bridge plate” much like a flat top.  I used a piece of cross grain Indian rosewood at .09” and formed an arch approximating the arch on the Gibson with a heating iron.  Then I used the topography created by the new braces to give me an approximate bridge plate size and cut and fit the rosewood so that I had a friction fit between the braces.  I figured that with a tight fit to the braces that the top under the bridge wouldn’t deform as much if it had support.  Once that was done it was a simple matter to make cauls and glue the plate in.  I was lucky that the Artist O has an oval sound hole that I could fit my hand in.  If this had been an L-4 the “f” holes would have been a much harder job. 

After letting the glue overnight it was time to string it up again and hope for the best.  The good news was that after a couple of hours there was no more deformation and even better news was that the bridge plate didn’t affect the tone at all.  It held tune and was actually louder than it had been without the plate.  Only time will tell if it was a complete success. 

Would I do it again?  Probably not at this price.  Was I sorry I took the job on?  Absolutely  not.  It was a challenge, but I feel that I got quite a bit out of it, and transformed a bag of kindling into a guitar again, a guitar that would be played and not just hung on a wall.  Jim Richardson may not look like Big Bill Broonzy, but he might someday be the coolest guy in the nursing home. 

Gibson Style O part 3

During work on the body I was also working on the neck.  As you might expect it was in the same kind of shape. A bad binding repair on the peghead, coupled with a piece of missing head stock overlay. The back was also very banged up.  When the fretboard was removed, big chunks of very brittle mahogany were torn out.  There was a v shaped maple insert in the center of the neck.  Only a third of the fretboard was left after I got the guitar.  It didn’t appear or smell to be rosewood, looking a lot like Macassar ebony.  The Fret House had already ordered a new “24 ¾” slotted ebony fretboard from Luthier’s Mercantile to replace the old one.  It was interesting to compare what I had left of the existing one and the new one to see that they were completely different.  Something I wouldn’t even have checked if I hadn’t read Dan Erlewine, Frank Ford and Tim Shaw’s article in American Lutherie Magazine on the different scales Gibson has used in the past.

The first thing I did on the neck was level it with sand paper stuck to the bottom of my joiner plane.  Then using a simple jig I cut the truss rod slot using a ¼” round bottom up-cut spiral bit.  I used a plunge router to make the cut because I could lift it up after the cut in the peghead, leaving wood in place for the screw in the cover.  The next step was to drill a ¼” hole to join the two slots.  The rod was a double action from Stewart MacDonald and the square ends of the rod were fit into the channel.

The fretboard was next.  I cut the board to shape to the 1 ¾” wide minus the thickness of the ivoroid binding, using the original as a guide.  After heating the binding in hot water I fitted it to the tight curves of the end of the board.  ¼” Holes were then cut for the mother of pearl position markers and the side dots.  With the glue dry a 16” radius was put on the fretboard and it was compression fretted with medium fret wire.

Since the neck had to be cut down and a piece of the peghead binding had been poorly repaired, I decided to replace it all.  By doing this and veneering the back with mahogany, the peghead almost looked new. I filled the missing piece of ebony on the front with dust and glue, taking care to fill the missing filler in the inlay, which thank God, was still intact.  The channels for the peghead binding were done with a router, with the exception of the two nearest the nut as the router bearing would have cut too much out.  Those channels were done with a Sloane purfling cutter. The peghead holes were then drilled to accommodate the new turners.

Before I put the fretboard on the neck, the angle had to be checked.  As you might have guessed 85 years had taken its toll and was at a much too shallow angle to be playable.  One of the things I did when I put the body together was to try and keep the original registration of the scrolls on the top and back aligned with the sides, but I realized that I’d have to slip the block a little.  I heated the back and head block with a silicone heating blanket and moved it as much as I dared, and took up the chisel to finish the job.  I took a full  3/16” off the heal of the neck to get the proper angle.  Luckily there was a lot of wood on the neck and I thought it actually made a better match to what would be a new svelte neck shaft.

Once I was satisfied with the neck I put the truss rod in, filled the gaps in the mahogany with dust and epoxy and glued the fretboard to the neck.  The neck was thicknessed with a Wagner safety plane and contoured with rasps and files.  The ebonized stripe in the center of the neck was lost and I thought it would very difficult to redo without a lot of head scratching so rather than spraying the stripe on with color, Jim and I decided to leave it out altogether.

After finishing the contouring, I sanded down to 320 grit and joined the neck to the body.  The neck angle had positioned the fretboard so that it didn’t contact the body by the sound hole, so a piece of spruce was fashioned to make up for the gap. After rounding the part of spruce that was under the exposed edge of the fretboard, it was barely visible.  When the glue was dry I re-contoured the body to blend in to the narrower board.  Jim had supplied mammoth ivory bridge pins, end pin, and Waverly’s with real ivory buttons, so that was a given.  I have one, yes just one, ivory nut that I’ve saved for about 30 years. And while I don’t put elephant ivory on my new guitars, nor would I put it on any modern guitar I repaired, I thought this is the instrument for it.

Next week:  Finish, set up and trouble shooting.