I have used Ziricote in several guitars and have never had to fill the pores first before spraying the finish but I had a bit of a surprise with Dan’s Ziricote. After the 12 sealing coats were sprayed and then cured for 24 hours, I lightly sanded the guitar to even the surface in preparation for topcoat spraying. Residue from the sanding filled many voids in the Ziricote and this is unacceptable as it doesn’t present an even appearance – the residue is lighter in color than the Ziricote.
So I used Zpoxy to fill the pores and this will delay lacquer spraying several more days. This is not a negative situation because there are builders who seal their guitars before they fill the pores (I typically fill first and then seal). The only issue is that I would have used fewer coats of sealer than 12 (probably 6) over pore filler. As I don’t want too much thickness in the finish, especially on the top, I may be able to cut back the topcoat lacquer from 12 coats to 8 or 10. I will monitor the finish after each topcoat spray. But first I must sand the pore filler to make sure all voids were filled in the wood grain.
The shiny pore filler has been applied and will be sanded off.
This post is not directly related to Dan’s guitar but I have to share meeting with Muriel Anderson, an internationally known guitarist and recording artist. She was actually booked in a small independent music store near Tampa for a workshop and concert last week. We attended this wonderful evening and spent a great deal of time talking to her about music and harp guitars.
Muriel and her harp guitar built by Mike Doolin.
A peak inside her harp guitar while changing the battery – fan bracing for a nylon string instrument.
Muriel graciously signed all CDs and books and gave every attendee a set of guitar strings.
Muriel has recorded a CD with flamenco duo Tierra Negra. It is called New World Flamenco and it is awesome – highly recommended!
Most custom guitars are finished with either nitrocellulose lacquer, UV-cured polyester, French Polish (shellac) or a polymerized oil varnish. With the exception of shellac, all of these finishes are harmful to your health and to the environment. The last six or seven years has seen the maturing of water-based lacquers that are durable and safe. I have been using a water-based lacquer from Crystalac for many years now. Although it is much safer than almost any other finish, I still take precautions to protect my lungs from any micro-particles or chemicals.
My name is Darth Vader and I am your father!
I have built a portable spray booth that I use for finishing. It sits on top of a table and has a powerful fan that sucks the overspray into a common A/C filter and has special braces for securing the body and neck.
The spray booth collects all the overspray and the fan sucks it into a filter. The plastic allows light to come through.
My spray schedule will consist of 12 thin coats of sealer (commonly known as sanding sealer) which is just thinned lacquer and then 12 coats of top coat lacquer. I will try to spray four coats per day three hours apart. After all the lacquer is applied, it will need to cure for one week before buffing.
I use an HVLP spray gun (high volume low pressure) and set my compressor at 50 psi.
I use a horizontal motion as I spray and overlap 1/3 of each spray.
Water-based lacquer sprays tiny beads on the guitar. Within seconds they spread out to form a solid coat. The build-up of 24 coats will result in a solid protective finish without adding much weight or damping to the top.
The daily spraying will continue for the next four days.
Many species of hardwoods have open pores in their grain. This presents a challenge when trying to finish them with a lacquer or varnish because these finishes do not fill the open pores very well and this leaves tiny voids that do not appear smooth in certain light. Ziricote and Ebony are closed-pore woods so nothing has to be done to prepare them for final finishing. Mahogany on the other hand is an open-pore wood and needs to have the pores filled before finishing. Many different kinds of fillers are used but the process is similar: force the filler in the pores with different strokes from different angle. I am currently using Zpoxy, an epoxy-based substance that does a great job at filling pores.
Preparing the neck for pore filling – the Ebony is taped off.
I mix the Zpoxy in mixing cups and spread some on the neck and work the filler in the pores using a thin plastic tool that I have shaped to conform to the neck radius.
I mix 1/2 part resin with 1/ 2 part hardener.
The Zpoxy is spread on the neck with a popsicle stick.
The plastic tool forces the Zpoxy in the pores.
After the pores stop accepting any more filler I do a final smoothing out so there are no peaks in the Zpoxy and I hang it up to dry.
The Zpoxy already gives the neck a finished look but it will be sanded off.
Once the Zpoxy dries, I will sand it back to the wood leaving only the filler in the pores. Sometimes I have to repeat this process to completely fill the pores (especially with Rosewoods) but a close inspection with the magnifying glass reveals the pores are sufficiently filled.
The guitar construction is now finished and ready for the lacquer. I must first clean the shop of excess sawdust and debris and then I will set up my spray booth.
The heelcap is the decorative hardwood on the heel of the neck where it joins the body. It is frequently an artistic statement by the guitarbuilder. Froggy Bottom Guitars has a wilderness scene on their heelcaps. I visited them years ago in rural Vermont where they have been building beautiful guitars for 40 years. My heelcaps, on the other hand, match the back’s wood and purfling to create continuity between the neck and body. I laminate thin Ebony and Maple veneers with Ziricote and glue them to the heel with a single clamp.
The heelcap laminates are clamped to the heel of the neck.
I leave slight overhangs around the perimeter of the heelcap and they will be sanded even with the heel after the glue dries.
The overhands will be sanded even using sandpaper and wood files.
After the sanding is finished, the neck is smooth all the way to the end of the heel.
The heelcap will butt against the Mahogany binding and the Ziricote grain will match the back.
One last task with the neck – the headstock. I mentioned the angling of the string channels in the slots of the headstock. I finished sanding them using sandpaper wrapped around dowels and now the wood veneers are exposed and are elegant.
A touch of color among all the natural wood tones. When the bronze strings pass over the channel the effect should be: well, effective!
During the building of a guitar, it is not unusual for the body to experience scratches, scrapes, and nicks. This is especially true with softwoods like the Cedar top. I use a magnifying glass and bright light to go over every inch of the guitar before the final sanding.
Examining the guitar with a magnifying glass from several angles identifies any scratches or nicks.
Nicks and scratches can usually be sanded out. Deep nicks must be filled first and then sanded. I use a mixture of luthiers glue and sawdust of the wood needing filling. Fortunately there were only two small nicks needing filling so this process only took a few minutes to complete. On the the other hand there were several scratches in the Cedar. A scratch is caused by a compression of the wood grain when focused pressure is exerted on it. To reverse the compression, steam is applied to decompress the wood and raise the grain back to its natural state.
I wet a shop rag and use my 40 watt soldering iron to create steam over the scratch.
As the steam reaches the compressed grain, it raises the grain until it’s even with the rest of the surface.
A proper angle of the soldering iron must be maintained in order to avert any burning of the top. I remember my old wood burning set when I was a kid – a lot of damage can be done in a few seconds!
After the body dries completely from the steam and sawdust filling, I do the final sanding using 220, 320, and 400 grit sandpaper.
The completed guitar with the bridge set in place.
One last task is to glue on the neck heel cap. I will use a lamination of Ebony, Maple, and Ziricote. I had set aside a piece of Ziricote for this purpose because I want to continue the grain pattern from the back to the heel cap.
Now back to the neck. Dan’s hands are not large (but they are very fine hands) so we need to shape the neck for comfort and maximum playability for him. We already have a shorter scale length so the distance between frets will be shorter than a larger scale instrument. I have elected to shape the neck similar to a James Goodall Grand Concert model. It is similar to a Taylor neck – I have used both templates and I really think Dan’s fingerstyle guitar suits the Goodall best.
My approach to carving the neck is using facets – carving to lines to eventually arrive at a “C” shaped neck. I first measure the neck blank width and depth and plot it on paper. I then use a compass to draw the “C” within the dimensions. I draw intersecting lines and measure from the center, ends, and top and then I transfer these dimensions to create facet lines on the neck.
Facet lines transfered from my drawing to the neck.
I use a hand plane, a spokeshave, and a cabinetmakers rasp to remove wood between the lines.
This process is repeated until there is a rounding of the neck. This hand plane removes the most wood and it is only used to “hog off” the initial facet.
I then use my neck template to start comparing to the shape at the first and tenth frets.
As the shape starts to conform to the template, I use 80 grit sandpaper sheets and use a “shoe shining” motion to round the neck.
The 80 grit paper and the back-and-forth sanding motion works the wood to the template shape.
When the initial shaping is accomplished, it is time to check the neck angle and orintation and to glue on the heel cap. First I need to finish the headstock. The bottoms of the slots in the headstock need to be angled toward the fretboard so the strings have a path to the tuners.
This hand plane removes the most wood and it is only used to “hog off” the initial facet.
I wrap 100 grit sandpaper around a 3/8″ dowel and work the angle until completed. Pictures to follow in the next post.
As the neck becomes rounded, I start using the template to monitor my progress.
The 80 grit paper and the back-and-forth sanding motion works the wood to the template shape.
I draw the basic outline of the angle on the headstock.
After the binding is installed and the final sanding is started, it is tradition to check the movement of the top to “predict” how responsive it will be. When my father was alive, he looked forward to holding the match in front of the soundhole while I tapped on the top where the bridge will be. Legend has it if the match is blown out by the air within the first two or three taps then the top is sufficiently responsive and will produce beautiful, complex overtones. I have passed the match-holding tradition to my youngest son Eric (who just graduated from Notre Dame). During the process he was Skyping his friend Shelly who happened to be in Mexico and could witness the process.
Eric is holding the match in the center of the soundhole while I tap.
The match was blown out on the first tap – we have a very responsive top!
In preparation for the topcoat finish, final sanding of the top, back and sides is accomplished in two phases. The first phase is to sand the binding even with all sides and I use a scraper first followed by a 100 grit sanding block. I then sand the backs and sides with a 150 grit sanding block. I use 220 on the top.
The back and cutaway after the first sanding. The Mahogany binding really compliments the Ziricote.
The second sanding phase will occur after I make sure all gaps are filled and all scratches are removed.
A view of the Cedar top and cutaway area.
The Ziricote back in low light – it is striking no matter what angle you view it.