There has to be at least one piano tuning expert out there who knows this better than I do....But here it is in a nutshell....
It's not really the glycerin that is the problem, but water. Glycerin certainly facilitates the problem, however. The glycerin when mixed with additional alcohol is able to penetrate into cracks, crevices and wood pores quite deeply. Glycerin on its own would not penetrate very well. The alcohol quickly evaporates, but leaves the glycerin in the pores. HERE IS THE PROBLEM: Glycerin loves moisture and it draws water out of the air to bind with it. As the water is adsorbed, it fills spaces in the cellulose (wood fiber) and increases the hydrostatic (essentially of the water) pressure within the wood. This expansion pushes the wood fibers outwardly and causes sections of joined wood, for example, to more tightly fit together. That all sounds well and good IF the expansion that occurs in the wood was a permanent change, but it is not and herein is the difficulty. The ability of wood (cellulose) to wick liquids is greater than the glycerin's ability to stay in place. So the water is eventually forced to leave the wood. The expansion also crushes the cellulose structure of the wood which is not reversible. Eventually, the wood may dry out again and you will have to do your magic glycerin treatment again and again and again. But in time, the introduction of the moisture coupled with the repeated expansion and contraction (i.e. getting wet and then drying) will rot the wood, and not only that, it will rust any metal, like nails, tacks, and brads that it comes in contact with. Any rust that is formed will shed from metal when the wood dries out and cling to the wood fibers. The more this expansion and contraction takes place, the more rust is formed, the smaller the nails get, and the looser the joints become. At a point, the nails lose their ability to fasten. Everyone has seen a rusty nail or screw in hole that just falls out of a hole - same problem. A GOOD piano guy would know the danger of this around things like tuning pegs. Needless to say, I am an advocate of doing things the right way and I don't advocate the use of snake oil (I mean and glycerin) for 'restoration'. If my car leaks oil it doesn't need a chemical to expand worn gaskets, it probably needs new gaskets. The chemicals that expand gaskets in cars like to stop oil leaks are often used by people who just want to push their problem off to the next owner. A piano tuner who uses glycerin is ALWAYS more interested in lining his pockets with your money than he is with the long term performance of your piano. Getting into an Orthophonic to seal the horn (or removing them if necessary) isn't easy, but we have marvelous things like silicone adhesives which, once they are applied, are apt to outlive the wood. Walt -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Andrew Baron Sent: Friday, February 09, 2007 11:46 AM To: Antique Phonograph List Subject: Re: [Phono-L] orthophonic/credenza question When you have a few moments, could you enlighten me with some additional information on what glycerine specifically does to the wood, short and long term? Thanks in advance, Andy Baron From: [email protected] Subject: Re: [Phono-L] orthophonic/credenza question Date: February 9, 2007 6:23:33 AM MST To: [email protected] Reply-To: [email protected] > But note that he advocates the use of glycerine to "rejuvenate" the > wooden > horn - and that glycerine is also used on pianos in the same way, > but by only > the worst, shoddiest tuners. It's a cheap, quick way to ruin wood. _______________________________________________ Phono-L mailing list http://phono-l.oldcrank.org -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.411 / Virus Database: 268.17.32/677 - Release Date: 2/8/2007
