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Some Questions and Answers

William R. Cumpiano


Look at it this way: the average guitar weighs around six or seven pounds: guitars are built to bear string tensions of ninety lbs. (when strung with nylon) to two hundred pounds (when strung with steel). It's safe to say that half of this stress is being borne by the neck and the other half by the box. When hanging from its strap then, the guitar's neck bears a far, far greater stress load from its strings than from just the weight of half of the guitar. It is inconceivable that attaching the strap to the peghead, which may add a two or three pounds of pressure will upset the apple cart.

Whether or not a guitar's weight on its strap is neglible, it is still a good idea to attach the strap to the heel: the guitar comes to rest in a somewhat more comfortable orientation across your body. There is no strap extending from your shoulder to the peghead distracting you and getting in your way. Finally, you need not fear that you're putting any undue stress on the neck whatever.

A strap pin hole in the heel (never put it into the sides!) can indeed devalue a collectible instrument, though. If you still want to install one on your 1948 herringbone D28, you could consider getting your technician to screw the strap-pin into a replacement heel-cap--and save the original.


I cannot conceive of any harm that an occasional dusting of baby powder can cause to a guitar. Baby powder is talc (ground-up soft stone) for the most part. Pumice, another ground-up soft stone, is used for polishing guitars. There was once a scare going around about the asbestos content in baby powder, but I can't imagine a guitar contracting cancer.


If your saddle is too tall it can cause the strings to break. It has to be quite tall, though, to break a lot of different strings. The optimal saddle height above the surface of the bridge is 1/8" to 5/32". Higher than that, and the guitar sounds louder--but then string breakage (particularly if you play hard) can become an real nuisance. As the saddle height increases, the "back angle" (the angle at which the strings drop down to the string holes) becomes more acute. As that happens, the strain on the string increases. On a bone or plastic saddle, dents are evidence of the pressure caused by the string's back angle. Their depth can indicate if there is an extreme situation happening there. If your saddle is indeed, too tall, have the guitar adjusted or repaired. It is generally a good idea to remove grooves in a saddle, since it can cause the string to snag rather than slide over the saddle when played energetically near the bridge.

Strings, however can also break with a normal-height saddle. Random string breakage can be tough to track down: many things can cause it. Sometimes, people just play too hard and they don't realize it. Not enough response from the guitar could cause you, while playing, to drive the strings past their stress limits. Your preference for phosphor bronze medium strings--an exceptionally high-tension string--suggests to me that you are trying to extract a lot of sound power from your guitar, even at the cost of having to deal with stiffer strings.

Other things can cause breakage: a misshapen groove in the nut can first pinch the string, then release its tension suddenly--and shockingly. If the top of the nut slopes too radically back towards the headstock, it can create a knife-edge situation there. I've remedied string breakage at the nut by replacing a knife-edge-shaped nut with a nut with a flatter top. You've just got to keep trying different things until your problem stops or is reduced to a bearable minimum.

Strings are, in fact, surprisingly similar in material and composition from brand to brand, so it's unlikely that you'll find a brand that will solve all your problems. You might hit upon a brand that uses a thicker core wire for your G, D or A strings. That might help, but you're not likely to prefer their sound: the thicker cores are harder to break but, being less flexible, they don't sound as good or intonate as well.


Your question is a tough one, since it's hard to sort out who's the culprit: you, the guitar or the strings. Your problem is multifaceted, and would require some careful analysis of your specific situation, to reveal its source.

You may be among the small population of individuals who have highly acidic perspiration, and you may be tarnishing strings quickly. The fact that you get the best service from gold-wrapped strings is some, albeit shaky evidence of this. Gold does not tarnish. Yellow strings may or may not contain gold, regardless of what the package says. I understand Maximus strings do, indeed contain gold. They might satisfactorily replace the strings you can't find any more. Also, classic strings are quite fragile, and a lot of energetic playing can do them in with dismaying rapidity. A lot of "bending," hammer- ons, or flat-picking of classical strings will indeed lunch them in no time.

Your instrument may not be very responsive or display poor definition, and may only sound good with fresh strings. I'm always amazed at how good a good guitar still sounds with beat-up, worn strings--and how quickly a mediocre guitar's sound deteriorates when the strings lose their initial brilliance.

It is a good idea to replace plastic nuts and saddles with bone and to set the intonation. I can only take you at your word that this was all done properly--indeed, classic guitars are special animals, and I would be less skeptical if it was a steel string guitar--if only because I know that good classic-guitar set-up experts are hard to find. But assuming that you are gentle with your strings (you can harm a classic string by uncoiling it from its package too roughly!), and your hand-made Velasquez or Gilbert guitar has been expertly set up, we can then go on to blame your strings. Most silver strings are a silver-plated copper/ brass alloy. Silver is softer than brass so it will sound less brilliant than all-brass, but silver tarnishes less. So take your pick.

The quality of strings owes less to their composition and more to their uniformity-- which usually translates to how many strings are rejected for imperfections during the manufacturing process, and how many actually get packaged for sale. This usually means more expensive strings (wouldn't you guess?). In the classical-string field, Savarez and D'Addario have among the highest selection standards and most sophisticated selection technology in the industry. You can get equal-quality strings in more modestly-priced sets, it's just that the chances of getting one or more duds is higher.

New strings go dead because of "dis-uniformity," where originally uniform strings get un-uniform due to tarnish, dirt encrustation, thinning-out at each fret position, and damage due to abuse. Uneven stretching is a problem, and sometimes a string can be renewed by simply dropping its tension and re-tightening to even out its stresses. Wiping strings often is important, especially underneath where crud tends to accumulate. Plastic scouring-pad material (the softest grade you can find) stroked gently along a string's length can do a fine job of freshening it up when it starts to turn marginal.

As regards the design of the wrapped strings, factors such as the size of the various filaments that make up the string, core and wrap, the angle of the wrap and the total mass will affect performance. Pity the string designer: the harder metals chosen for the wrap (i.e. brass, nickel) produce more brilliance, but they tend to fray faster and become loose with less effort. The softer metals (i.e. silver, gold) sound mellower but hold their integrity longer. The thinner the core, the greater the flexibility and the better the intonation, but the weaker the string. A thicker, more massive string gives greater power, but being less flexible, intonates less accurately.


The only person supplying custom purflings in the is Michael Gurian. He can make single strip or multi-laminate purflings in wood or high-quality fibre, and marquetry inlays to your specifications. You must order in sufficient quantities to make it worth his while, but I've found that his minimums are consistent with the quantity that a busy luthier can use up in a year or two. [Michael Gurian, GURIAN INSTRUMENTS, 206 3rd. Ave. South Seattle WA 98104 (206) 467-7990/ (206) 467-8288 fax


The "fully" of your question is a puzzler. You obviously haven't been "fully" satisfied with whatever brand or system you've tried. Are you sure that your problems aren't user-induced? Or that your environment or application schedule is not conducive to a satisfactory result? The best lacquer system in the world will not be "fully" satisfactory to someone who lays it on too thickly, or doesn't wait long enough between coats (or before polishing) or who has the wrong air cap or needle on their gun, or whose lacquer brand needs a bit of castor oil added for more flexibility (to avoid checking), and so forth. There's a lot to know before you can get "fully" satisfactory results. What brand to use is the least of your problems. By the way, my secret to a film that doesn't sink into the pores after the guitar is delivered: I use an absolutely minimum amount of sanding sealer, I apply no more than two coats a day and wait three weeks or longer before polishing it out.

Does anyone know of an adhesive that will hold pickguards down for both old repairs and new applications?

I had despaired of ever finding a satisfactory answer to that question. Over the years I've tried dozens of spray adhesives that all worked fine over the short term, but failed over the long term. But I have reached the end of my quest: for the last three years, I have been using, not a spray, but an adhesive that comes in the form of a double-sided film-- and it works wonderfully well. It is Scotch 467MP Hi-Performance Adhesive. It is only a few mils thick and it grabs like the dickens! A roll costs about $40 and lasts and lasts. I buy it from a large East Coast art-supply company CHARETTE, PO Box 4010, Woburn MA 01888-4010, (800) 367-DRAW

Is there a general order of thickness for guitar tops as a function of the types of wood used? Do stiffer woods allow thinner tops if the same bracing is used? What is the general order of mechanical thickness for spruce, redwood, mahogany, koa, maple, etc.?

Aye, there's the rub! You've hit upon all the $64,000 questions! If I could simply rattle off the number of thousandths in each case, it would all be so easy, wouldn't it? But I can't, since there are even more parameters to consider: soundbox size, expected string tension (as determined by string material, length of scale, and height of strings over the soundboard) and last but not least, the natural stiffness of the specimen that you actually are using--which can vary enormously. Besides, "general order" thicknesses are useless, because variations of several thousandths of an inch can increase or decrease stiffness dramatically (stiffness varies as a CUBE--to the third power--of cross- sectional height). An extended article is a better format for answering these questions than a question-and-answer column. I'll add it to my list, to be published here in the near future.

Is there general agreement about the relation of soundboard tap tones relative to back tap tones? If so, how much higher or lower should the back tone be than the front?

In a word, no. I certainly don't recognize it, and several professional builders I asked said that they also don't worry about it at all. The Catgut Acoustical Society has, if fact, determined quite specific relationships between the top and back violin plates, and what they are (or should be) on good violins. But alas, the rules for violins are not at all applicable to guitars, their acoustic architecture being so totally different. To date, no one has published any definitive rules to that effect on the guitar--but I invite comments to the contrary. I asked Tim White, past editor of the Journal of Guitar Acoustics, who made the following observations (with some of my added comments):

A "Principal Rule," so to speak (if there is any to be noted for the acoustics of the guitar), concerns precisely where the "rum jug" resonance falls on your guitar. This is the fundamental air/wood resonance of the soundbox, which can be clearly elicited as soon as the soundbox is enclosed during the assembly process, and later, after the guitar is strung up. The way to determine the guitar's fundamental resonance is to hum loudly across the soundhole, taking care that your head is to one side of the soundhole so it doesn't block or slow the flow of air in and out it. Hum siren-style across the baritone spectrum, and at about G (same as third fret, sixth string), the guitar should start to shake, to "sing back at you." You'll note that if you thump the guitar sharply at the bridge, or in the middle of the back, that same note can also be discerned quite clearly amidst a jumble of others that are not so distinct. This note is a key that will indicate the overall stiffness of the entire system. It does not indicate any information on the high frequency resonances of the box, but will give an "in the ball-park" reading of where the guitar lies, relative to similar observations on good guitars. On Martins, the rum-jug resonance falls exactly at G (99 hz), but on other good guitars, the note can vary up to a semitone up or down. In order to sound at G, small guitars must be built very light, and large guitars, quite stiff. On classics, a good note to aim for is A. On any guitar, if it sounds as high as B, the guitar will sound tinny and tight, and at F or below, it will sound tubby or flabby. You can change the resonance down if it is too high by scraping the plates (start at the outer edges) and/or reaching inside with a plane and "mining for wood" at the braces. Quite a lot of material needs to be removed to make a noticeable shift, so if you're way off the scale, it's time to remove the back again (easier before the glue has set hard) and remove some fans or lower face braces--or a back brace (Tim says that each major brace contributes a semitone to that rum-jug resonance). I don't know anything that you can do if the resonance is too low. Another interesting thing Tim pointed out was that the fundamental SOUNDBOARD resonance starts to speak roughly an octave above the rum jug resonance. On classics with symmetrical patterns, that resonance is associated with a "see-saw" rocking motion of the face with it's centerline lined up with the guitar's centerline. This alignment makes this motion rather inefficient for sound production. On the x-braced steel-string guitar however, the fact that one arm of the x is deeply notched in the "up" direction (i.e, one x-brace arm is stiffer than the other) and that the lower face braces are skewed un-symmetrically, the axis of the soundboard rocking mode is itself skewed off to one side. This, Tim says, makes the first rocking mode far more efficient. To my mind, this may explain some of the output difference between the two types of guitars, and why so many good classical builders have stopped using a strictly symmetrical soundboard bracing pattern.

Why are steel-string bridges located at the top of the lower bout and classical bridges generally in the middle of the lower bout? What are the implications of the answer for the general effects of steel strings versus nylon strings on bridge placement?

Classical guitars always have twelve frets to the body. Most steel string guitars have fourteen frets to the body. If you were to move the steel-string scale down so the twelfth fret met the body, the bridge would correspondingly move down closer to the middle of the lower bout. Coincidentally, you move the bridge away from the apex of the x-brace, which places it in a more compliant part of the top. This yields a fuller, more open, rounder-toned sound--which is what endears 12-fret steel-string guitars to many players, especially those who don't mind sacrificing some upper-fingerboard accessibility for it.