Conference napalm::guitar

re           <<< Note 2670.0 by RICKS::CALCAGNI "L'Angelo Minestronio" >>>
>                        -< Finish checking and crazing >-

>    Ever notice those fine surface cracks in the lacquer on an older (50's,
>    60's) guitar?  Usually they run across the face of the instrument, perpendicular
>    to the string; another common spot is across the back of the neck, especially

	my guess is that the ones in this direction are due to string 
tension and that 30~40 years of such tension is going to compress the 
face of any guitar archtop, classical or even a solid body.

>    near the headstock joint.  Gibson's seem especially prone to this.  I
>    believe the official term for this effect is "crazing" and is caused by
>    the inability of old lacquer to respond to expansion and contraction of
>    the instrument.  "Checking" is a more serious version of this effect in
>    which cracks criss-cross and form tiny islands or "checks".
    
>    I was wondering if anyone had any advice re reducing or dealing with
>    this stuff.  I think I take good care of my instruments; I store them

	I think the conventional answer is to use a  "softer"  or more 
 "compliant"  finish, but that is supposed to dampen tone (highs).  
Maybe the StewMac shop tips would be a good source of info ?

>    in the case, usually in rooms fairly comfortable in temp and humidity,
>    never leave them in the car overnight, etc.  Nevertheless, I still have
>    trouble with crazing and checking.  Sometimes I'm not even sure if it's
>    something I've done or if the instrument had the problem already and
>    I just didn't notice it before.
    
>    Besides the obvious (avoiding extremes of temp, etc.) are there any
>    practices to help reduce this stuff?  Does polishing help? (I rarely polish

	Rate of change is probably more harmful than absolutes (within 
reason), I'd guess that humidity is a bigger factor than temperature - 
especially if you let it get too dry too quickly, like the start of 
the New England heating season )-:

>    my guitars)  Do you have to expect some of this in older guitars no matter
>    how much you pamper them?

	to a certain extent, Yes  - -  and its part of the

		"beauty of age"    

	so enjoy it (-:


>    /rick

	Reg

    These checks are almost invariably caused by temperature changes. Extra
    polishing doesn't help (it may in fact hurt).
    
    The age of the instrument doesn't have much to do with it either,
    except that the older it gets, the more likely it will be exposed to
    temperature changes. Some types of finishes and some model years seem
    to be more prone to it, and some woods are worse than others (Rosewood
    is particularly bad).Lacquer is much more susceptible than poly.
    I have had guitars from the '40's with none at all and guitars from the
    '80's with tons of it.
    
    I try not to have guitars shipped to me during very cold weather. I
    once shipped a mint '70 JS during January by UPS ground and it arrived
    in CA completely checked (UPS paid for a refinish). I always leave a
    guitar in its case for several hours after it's been in the cold before
    opening it. If you open a guitar case and the guitar hazes or blushes,
    close the case immediately. If you're doing gigs where it's not
    possible to let the guitar warm up slowly, play a cheap poly-finished
    model on cold days :-)
    
    
    Fine crazing that runs along the grain is usually considered a minor
    defect. Large, cross-grain checking is worse and significant amounts of
    it will decrease an instruments value.
    
    
    Danny W.

    Btw, low humidity more often causes grain splits, where the wood itself
    separates along a grain line. 
    
    Danny W.

    Although in general it is rapid changes in temperature that cause and
    exacerbate checking, temperature extremes can also cause it. It is best
    if instruments are never exposed to temperatures below 40 degrees F and
    above 90 degrees F. I have seen guitars that became extremely checked
    after being exposed to below freezing temperatures overnight and then
    warmed up very gradually.
    
    Storage at normal household temperatures of 50-90 degrees F should not
    be a problem. It is best to avoid storage against outside walls, near a
    radiator, heating vent, stove or fireplace, and it is always a good
    idea to keep the guitar in a hard case when it's not in use. If I
    remember, I try to put Herco "Guard Fathers" into each case in the
    winter, but I haven't figured out if they do anything or not.
    
    There are some areas on a guitar that seem especially prone to
    checking, I often see guitars with checking behind the nut and at the
    heel where end grain is exposed, even when the rest of the guitar is
    completely unchecked. The rims of archtops are under a lot of stress as
    they age, especially as the binding shrinks and the wood tries to
    regain its original shape. The waist, shoulders and hips will often
    develop cracks, and checking is common even from ordinary temperature
    changes.
    
    There is a type of cross-grain checking that occurs below the varnish,
    appearing as bright lines, typically from edge to edge on the affected
    wood. Although it looks bad, it cannot be felt on the surface of the
    guitar. This type of checking is often not visible at all from certain
    angles or under some lighting conditions. I have found that some
    occurrences of this will disappear and reappear during the year as the
    guitar shrinks and expands from humidity changes. As these lines become
    visible, it seems as though the humidity is the cause of the checking,
    but in fact the checking has merely been hidden. I once had a guitar
    (another JS--a '66) that had many of these lines around the back of the
    neck--they were clearly visible for three or four months each year and
    impossible to detect the rest of the time. Some cases of this can be
    cured with a heat lamp, though there is always the risk of doing more
    harm than good.
    
    Although I prefer my guitars not to have weather-checking, several of
    my favorites have quite a bit. I've tended to become more indifferent
    about it as I (and my guitars) get older. I still avoid guitars with
    highly crazed surfaces, but mild to moderate subsurface checking and
    even mild surface checking doesn't bother me as much as it used to.
    Fine archtops have become scarce enough so that it seems foolish to me
    to discount one because of some checking. 
    
    
    Danny W.
     

    Thanks Danny, lots of good info.  Btw, could you explain the terms
    checking vs crazing?  I had my own idea, but doesn't necessarily seem
    consistent with some of the things you've said.
    
    /rick

    My dictionary defines "check" as a small crack or chink, and "craze"
    as a network of fine cracks. In the guitar world, there is no
    universally accepted use of either. I tend to use checking to describe
    any of this and crazing to describe actual cracks in the finish. I once
    had someone ship me a guitar after telling my it had "lots of grain". I
    sent it right back after discovering that he meant that the front was
    heavily crazed.
    
    Danny W.

    In wood working, "checking" is a crack in the wood, most commonly
    ocurring at the end of the grain, and happens as the wood dries.  Buy a
    2X6 at the lumber yard, leave it outside for a year, and it will check.
    
    Different species of wood are more or less resistant to checking. 
    Also, the finish can help the wood resist moisture loss, reducing the
    tendency to check.  
    
    Crazing is something that happens to the finish, the tiny hairline
    cracks that are the topic of this conversation.  
    
    
    				Norm Abrams