Hi Chuck, Do you use the solvent based cc or the safer version available James James Grebe Est. 1962 Piano Tuner-Technician Creator of Custom Caster Cups Creator of fine Writing Instruments www.grebepiano.com 1526 Raspberry Lane Arnold, MO 63010 (314) 608-4137 Become what you believe ----- Original Message ----- From: "Chuck Behm" <behmpiano at gmail.com> To: <pianotech at ptg.org> Sent: Saturday, January 02, 2010 7:16 AM Subject: [pianotech] Misconceptions concerning contact cement for use withkeytops > List - As I've read through the posts concerning methods to glue keytops, > I've been concerned about the misinformation concerning the use of contact > cement. I am not an authority on the use of either PCV-E glue, or Mike's > European glue, but I do have concerns about their relatively weak bond. > If, > as Debbie L.'s testing seems to bear out, keytops glued with either of > these > adhesives may be removed with "easy" to "moderate" effort with a flat > bladed > knife, how much effort would it take on the part of a determined 4 or 5 > year > old to removed said keys? I would very hesitant to put a set of keytops > into > a piano in a home with small children with no more assurance than that. > Kids, being the inquisitive creatures that they are, at some point will > try > pushing up on the overhang of the naturals when no one is watching. God > forbid one should pop off, because if it does then the "Hey Suzie, look > what > I can do!" phenomenon sets in. The classic case for me was the customer > with > a set of twin 4 year old boys, who discovered what they were able to do > when > left unattended for 15 minutes by their babysitter who was texting her > boyfriend and watching a movie in the adjacent room. After one key had > been > popped off, 51 more followed. When finished, the two boys craftily > returned > every keytop to the correct key, and neatly straightened them out, so that > to the casual observer, nothing had been touched. The kicker was, when the > mother discovered what had been done the next day when she sat down to > play > the piano, the boys claimed that the "babysitter must have done it!" These > keys, by the way, had been replaced several years by another technician > before I was hired as her tuner. I'm not sure what adhesive had been used, > but it obviously didn't do the job. > > Anyway, I just would like to set the record straight as concerns the use > of > contact cement (for molded keytops with fronts). What I like about contact > cement is that used correctly, there will never be this type of failure. > Plus, it requires the use of no clamps - just a 30 second squeeze in a > cork-faced vise will do the trick. Let me therefore take some of the > comments made, and respond to them. > > (I have, in the past, tried contact cement but I hate the vapors. Debbie > L.)* -* A fair observation, but one that is not difficult to deal with. > Unless you're working in an area the size of a broom closet, the vapors > may > be dealt with by providing a bit of cross ventilation. A fan, placed off > to > the side so that a gently breeze blows across the work area, will do the > trick. The vapors are not nearly so intense as CA glue. The vapor given > off > by polyurethane affects me more than that of contact cement. > > (Some seem to have no problem with it, but I've seen enough failures to > not > want to find out why first hand. Ron N) - Two reasons come to mind Ron. > Number one, the top of the keystick must be coated twice. The first coat > will largely soak into the wood. The second coat, applied at least 15 > minutes later, will provide the bond. If only one coat is applied to the > wood, the bond will not be strong enough to prevent failure down the road. > Number two, if too much time elapses between coating the surfaces and > bonding them together (refer to the bottle, but something along the lines > of > 2 or more hours) the bond strength will not be strong, if the surfaces > indeed bond at all. > > > (Contact cement works well but it's toxic, and since there are other good > options it seems best not to use it. David Weiss) If by toxic you mean > you > wouldn't want to drink it, you're probably right. However, if I'm not > mistaken, I believe there are a lot of things used in the shop which would > fall into that category. Lacquer thinner, CLP, mineral spirits, etc., come > to mind. Come to think of it, I don't believe that I would want to pour > myself a glass of PCV-E to chug either, although it does look temptingly > like a milkshake! > > (I don't care to use contact cement as I find the failure rate high and > the > glue > itself can mar the surface of the keytop if it gets on there. David Love) > Again, as I commented to Ron, if you simply coat the keystick once, it > will > not provide adequate adhesion. As to the fact that contact cement will mar > the surface, that is exactly the reason it works so well when applied > correctly. The cement reacts chemically to the plastic keytop, and bonds > with it in a way that PCV-E glue will not. The reason PCV-E wipes off so > easily, is because it does not interact with the plastic. That is also the > reason keytops thus applied may be removed with "easy to moderate" effort. > > This can be a pain, I'll admit, for the first-time user who doesn't know > how > to correctly apply contact cement. With correct procedures, however, you > will not get the cement on either the tops of the keys, or your fingers. > > > (Or in the case of contact cement, apply pressure to the top and front at > the same time. There is currently no clamping system available to do this > (that I know of) and I don't believe the old Oslund system addresses this > issue either because one of our clamping systems is an Oslund clamping > setup > and I don't see it as an option. Mike Morvan) One of my points about using > contact cement is that clamping is unnecessary. Once the keytop with the > front is put in place (again, methodology is everything), the front is > secured in place with a downward pressure of the key on the edge of the > bench. The top is secured by placing the key momentarily (while the next > assembly is being made) into the cork faced vise. After this brief > pressure > is applied, no further clamping is needed. > > (Also, it is far too strong a joint making future removal for > repairs/replacement a nightmare. Debbie L.) Debbie was speaking here of an > acetone based adhesive at this point, but I've heard others express this > concern as regards to contact cement as well. Removal of keys bonded with > contact cement is done with the application of heat via a flat iron. A > lightly dampend cloth (to prevent the iron from adhering to the plastic) > is > placed in between the iron and the keytop, and heat is applied for 10-15 > seconds. After heating the keytop will peel off with a small putty knife. > > Occasionally, while working on a set, I'll drop one and chip the corner, > or > in filing I'll chip off a bit too much at the notch, so I have a extra set > of keys for just such an occasion. > > Again, as I stated before, whatever works for you is what's best. I just > hated to see people not try a method because of misinformed opinions. In > that I've used contact cement successfully for 35 years, I know that it > does > work. Chuck Behm > > > > > > ** > > ** >
This PTG archive page provided courtesy of Moy Piano Service, LLC