U-Beaut Hard Shellac - Once Bitten, Twice Shy

I didn't want to die wondering whether U-Beaut's Hard Shellac could have been the answer to my finishing dreams and I experimented with it on this little Claro Walnut/Engelmann Spruce 12-fret double-0, destined for my own use. Having been distracted by other projects recently I've only just strung the guitar up and, although it's still a little tight and is yet to have its initial fret job and setup, it sounds very promising already. What's more, I love the way it looks - up to a point.

Reports from those who had used an earlier formulation of this finish were encouraging, but there were occasional angry mutterings about serious crazing which sometimes materialised weeks or even months after application. In response to criticism, the manufacturer added a plasticiser to the recipe and re-released the product, advertising the fact that it was now suitable for musical instruments. I certainly found it a dream to spray after reducing it 50/50 with denatured alcohol to a 2lb cut and, after waiting three weeks or so for it to fully cross-link and harden, I was able to rub it out to an impressive shine. I was an instant but cautious convert! My optimism was tempered by the recognition that any finish - particularly a shellac variant - has to prove its resistance to use and abuse over time before it can be declared commercially viable. With neither use nor abuse to blame in this instance, my hopes have been dashed already however and, after six months, the finish on the neck of this guitar shows the first barely discernible but unmistakeable signs of the same crazing which so frustrated (some) users of the earlier formulation. There's an equally faint suggestion of the same thing happening at the waist on one side and there's no telling if it will worsen or appear elsewhere over time. I must say, I'm not too upset though; it was a risk I was willing to take and at least it's answered the questions I had once and for all - in my mind anyway.

Interestingly, this Australian product has recently been added to the inventory of one of the leading U.S. lutherie suppliers and there's been a good deal of excited chatter about it on one of the on-line guitar building forums. Based on my very limited experience, I can only urge caution; either the additional plasticiser hasn't been entirely successful in curing the crazing problem, or skilful application is absolutely critical to success. Although I was at pains to spray thin coats, waiting an hour or so between them (it was a hot day), it just may be that the ambient conditions at the time weren't ideal, or that my rudimentary skills with the spray gun weren't up to the task. Perhaps those applying it as a french-polished finish will have better luck, but after this experience, I'm fearful that the results are likely to be unpredictable at best - not a recipe for good customer relations. For the time being at least, I'm inclined to stick with the water-based KTM-SV I discussed in my previous post.

Cheers

Pete

KTM-SV - The Bee's Knees

As I'd hoped, the top coats of Grafted Coatings' KTM-SV went onto my OM beautifully, particularly after I'd added some distilled water to the finish prior to spraying. The advice I'd read suggested adding 1 ounce of distilled water to a quart of finish which equates to around 30ml for us metric types. I used approximately half of my quart tin which should leave enough for the Australian Blackwood/Sitka Spruce triple-0 waiting in the finishing queue.

Other than it being an opportunity to become better acquainted with my spray equipment, I learned that acceptable results are probably more likely when the temperature is lower and the humidity higher than it was on my first day of spraying. With the temperature climbing to around 35C through the day and the relative humidity sitting on 20%, I was probably foolish to have proceeded and it was difficult to achieve the wet coats I wanted. I'm sure my inexperience played a large part in the less than perfect results I had with the initial coats too. Although it didn't dry with the gritty appearance that suggests that the finish has dried en-route, between the spray nozzle and the guitar, I suspect it was dry very shortly thereafter, before it had a chance to self-level completely. As a result, some "orange peel" was evident after the first couple of coats. With more practice, the addition of the distilled water and cooler, more humid weather on the second day of spraying, however, I was pretty happy with the appearance of the later coats straight off the gun.

I waited a couple of days to level sand and a few more days before attempting to polish out the finish. Without a buffing wheel at my disposal I use a random orbital sander and Surbuf polishing pads purchased from Lee Valley Tools in the U.S. The polishing compounds I used are made by Autoglym and are branded 03B Fine Abrasive and 02B Ultrafine Renovator. They replace the Meguiar's products I used previously which I found unsatisfactory for my purposes. After a week, the finish on this guitar is HARD, and it's a slow but satisfying process sanding through the grits then rubbing out to a high gloss with the polishing compounds. Perhaps as I hone my skills I'll think about building a buffing wheel, but I feel there's less chance of buffing through to the wood with my current method, which is certainly slower but much less prone to burn-through.

Having progressed this far, I'm increasingly confident that the KTM-SV is the safe, environmentally-friendly finish I've been looking for. Those who've used it for some time and have had instruments out in the real world for two or three years have reported no issues with it which strengthens my belief that this is the ultimate finish for the the health-conscious amateur luthier with limited resources and a less than ideal working environment. For an even more low-tech approach, I understand it can be brushed on which makes this product suitable for even the rawest of beginners.

I'll post glamour shots soon - minus the scantily-clad model - when the guitar is strung up and ready for delivery!

Cheers

Pete

OM Nearing Completion

Click for a larger view

With its new owner due to visit in a couple of weeks, I've been spending a lot of time lately preparing this guitar for finish.

Here's a shot taken this afternoon after shooting a couple of seal coats of 2lb-cut de-waxed white shellac. Prior to spraying, I inflated a couple of party balloons inside the body of the guitar to seal off the soundhole and the soundport, preventing any contamination of the interior.

Given my limited experience with sprayed finishes, it's a case of "so far, so good". I arrived at what I think was the right combination of spray gun settings more by trial and error than anything else. Setting the correct air pressure at the compressor, then adjusting spray pattern, air flow and material flow at the gun took some patience but, as with anything unfamiliar, the secret lies in constant practice.

Without a dust-free environment to work in my finishes are never going to be flawless but, under the circumstances, I'm pretty happy with the results so far. My hope is that the top coats of KTM-SV are as easy to apply as the shellac seal coats were. I guess I'll find out over the next few days!

Cheers

Pete

The Cautious Approach

The way I see it, pledging the guitars I'm currently constructing to keen players free of charge has a dual benefit. Not only is it a nice thing to be able to do for someone who might otherwise never own a handmade instrument, but I also get to have my guitars road tested under real-world conditions. With instructions to play the hell out of them and subject them to the rigours of everyday use, hopefully they'll take this treatment in their stride and I'll be more confident of approaching guitar building as a commercial enterprise, albeit in a limited way. Were I to keep the guitars for my own use, I'd really be none the wiser; they would see little use and, when they were played, I'd follow past practice and handle them with kid gloves. I'd rather not make the assumption that life for a guitar is always that easy! I have sold several instruments in the past, but I feel I did so in ignorance of the risks and the potential for conflict.

Having built around 15 electric and acoustic guitars over the past 20 years, I know that structurally they'll hold up just fine. The area in which I do need reassurance is with the finish I'm about to use for the first time. KTM-SV, a water-based urethane, is receiving great press from those who've tried it, but I'd like to see for myself how it stands up to use and abuse over, say, 12 to 18 months. I can extrapolate from there and make an assessment as to what the longer-term prognosis is likely to be. The manufacturer, Grafted Coatings, has this to say about KTM-SV:

KTM-SV Spar Varnish wood finish is a waterborne, oil-modified, self-crosslinking urethane system. It features high quality, low film yellowing, excellent chemical, mar and scuff resistance, and is specifically designed for finishing wood. Because of its inherent oil urethane characteristics, the user can expect excellent flow, leveling and penetration into porous wood surfaces. Applied by spray or brush, maintaining high solids in the coating allows for good film build and fewer coats to apply.

In my search for a safe, environmentally friendly finish material, I've found any number of products which sound good on paper, however, the reality is that the demands placed on a finish destined for an acoustic guitar are unique. Tops, backs and sides are in the region of 2mm to 3mm thick and expand and contract unhindered. Not only does the finish need to be wear and scuff resistant, but it must also be flexible enough to withstand these changes in dimension on a daily basis. Add to that the guitar-buying public's expectation that their prize instrument should have a mirror-like gloss and the list of candidates shrinks significantly!

Cheers

Pete

Fretboard Completed

Here are some shots of the completed fingerboard which I've slotted, inlayed and bound.

The benefit of some years of experience is that I've come to recognise and accept my own limitations. A more ambitious inlay design would in all likelihood stretch my patience and there's every chance I'd put off completing the job. The other advantage of a simple inlay design is that it looks so darn good, at least to my eyes! Less is more as they say.

The edges of the fingerboard are bound with black and white veneers and a 1mm outer layer of koa. Once the fingerboard was bound, I ran it past an upturned spiral downcut router bit to form a rebate along the edge that will adjoin the neck shaft. Black and white purflings were then glued into this ledge.

Cheers

Pete

Carving the Heel

Pictured here is the result of a couple of hours spent shaping the heel. This is as far as I'll proceed for the time being; I'll carve the neck and fine tune the shape of the heel after the fretboard has been glued to the neck shaft. I've chosen to rough carve the heel prior to attaching the radiused fretboard as it's easier to secure the neck in a vice or clamp it "heel up" to a benchtop without it.

I use a template to pencil in the shape of the heel where it will meet the sides and a second template to mark the outline of the heel cap. Although the intersection of the heel and the sides is critical to the accurate alignment of the neck with the centreline of the body and is crucial in establishing the correct neck angle relative to the bridge, there's a large degree of latitude where the shape of the heel itself is concerned. It's an ideal opportunity to inject some creativity and there are some wonderful examples where luthiers have done just that. Personally, I prefer to keep it simple and a graceful set of curves and a slim, refined look are my primary goals.

I carry out the initial shaping using a variety of chisels, then move to rasps and files. As the heel approaches its final shape I switch to scrapers and sandpaper. Shadows cast on the heel while holding the neck up to a bright light help identify any remaining lumps and bumps. Although I'm aiming for symmetry, I'm not obsessive about it - I'm happy to rely on visual cues such as this to highlight any inconsistencies.

Cheers

Pete

An OM for Maurice

As a music lover as well as a guitar builder, I can imagine no greater reward for my efforts than getting my instruments into the hands of great players. With that goal in mind, here's one of the instruments I'm working on which I look forward to sending to friend and musician Maurice McGovern in Melbourne.

Soundports like the one pictured are becoming commonplace on custom instruments and, having added one to an old guitar of my own, I can vouch for their effectiveness. US builder Matt Mustapick has this to say about soundports:

This concept came originally from the great classical maker Robert Ruck, who puts two small holes on each side of the guitar, very close to where the neck joins the body, rather than one larger hole. The main advantage of the soundport is that it gives the player a "front row seat" to enjoy a strong direct signal from the soundbox. This feature takes nothing away from the forward projection of the instrument. From 20 feet away the guitar is just as loud. For anyone closer to the guitar, it adds a great deal of richness to the sound, owing to the dual sound source which creates a stereo field.

The combination of rosewood with koa trim is one of my favourites and I can't wait to see the effect when a finish is applied; the rosewood will darken considerably and the curly koa will really come alive. The small clamps I use when gluing kerfed linings came in handy for pre-gluing the purfling lines to the koa bindings prior to bending them in my Fox bender. I used Titebond 3 for this job and there was no sign of delamination which can happen with regular Titebond.

The purflings around the perimeter of the top and back are comprised of black-dyed maple and natural maple veneers with a 1mm mahogany centre piece. The five veneers were glued up as a sandwich using Titebond 3. I then cut the sandwich into strips on the bandsaw (a table saw with thin-kerf blade would be better) and ran them through my thickness sander prior to bending. On future guitars I'll substitute black fibre for the black maple; the maple gave way on the outside of some of the tighter bends. Luckily, I took the precaution of bending a few spares at the same time.

The overlay on the rear of the headstock strengthens the splice - not that it really needs it - and also obscures any glue line where the headstock joins the neck shaft. It's a much cleaner look as well as another excuse to use more of that beautiful koa!

Cheers

Pete