I just put on a tooth guard on an old Link STM (which was completely missing), repaired the white tooth guards on couple of Brilharts, and put a baffle in an Otto Link Master.

For the STM tooth guard, I put Scotch tape down both sides of the pocket in the metal mp.  I then brushed the MMA into the pocket and built up layers of black plastic by dipping a small artist's paintbrush in MMA and then the black acrylic powder.  It was going slow, so I directly mixed the powder into the MMA to create a thick paint and applied that way.  It looked bad, but I then used some very small stainless sculpting tools to level out the goop and press it into place.

I tried to use the old body-and-fender trick.  Bondo goes through a "cheese-like" consistancy for 10 or 15 minutes.  During this time a rasp or "cheese-grater" type of file can quickly remove excess material.  With the acrylic paste, that time window is about 1 minute.  During the soft phase, it comes off fast, but it gums up whatever you're using.  Once it sets, the material is very hard and the filing goes much slower.  I found it difficult and time consuming, especially when being careful not to mar the finish on the metal mp (which I masked with Scotch tape, watched very carefully, and replaced when it got worn).  Only problem was a couple small pinholes from bubbles in the mixture.  All-in-all, a success.

I used white acrylic powder to repair the white tooth guards on two Brilharts.  One of the original pads was worn all the way through to the black mp body.  When adding white "paint", I noticed that I was picking up tiny amounts of the black body pigment from the bottom of the gouge.  Therefore, the patch is not as bright white as the original (something that I noticed but most people probably would not based on the fact that it's an old mp).  What this tells me is beware of MMA.  It does have the ability to dissolve the mp, even though slightly.  The white patch on the Brilhart that wasn't worn down to black looks perfect.

The final project was adding a baffle to an ancient Link Master tenor that had been hogged out by a prior owner.  Apparently, somebody either didn't think that it played dark enough or that, since removing material is the easiest alteration, that's what they tried.  Sort of a variation of the theme, when all you have is a hammer, everything looks like a nail.  Anyway, I thought I'd add a mild little baffle and see if I liked it better on my C Melody.  I'm hoping to update the horn's sound from the teens to the 1930's.

I cleaned out the interior with alcohol.  I mixed the acrylic powder into a runny putty and poured maybe 1/2 tsp. into the mp.  The stuff sets up so quickly that, again, I didn't have too much time to work it with the sculpting tools.  I got it quite close to what I wanted, but once it was hard I was then faced with a lot of tedious filing and sanding.  The baffle was close to the tip rail and not very smooth right there, so I had some annoying chirping during the intial testing.

Fortunately, after working the piece for a little while, it popped loose.  I could then work the piece on a diamond grinding stone and emery cloth on the bench, much like facing a mp.  I could hold the piece to get a perfectly flat baffle with a nice even drop-off.  I could even work the edge by the tip rail quickly.  When I was done, I painted both the back of the baffle "insert" and the mp with MME and dropped it into place.  It got a little sticky, but the material doesn't reconstiture into a putty at all.  The final clean up was easy.  Again, I had some pin-holes from bubbles in the mixture, but nothing major. 

I'm happy, but then what do I know?

I talked with my dentist an my appointment this week about MMA.  He's worked with it a lot and agreed that he hasn't really seen too many hard and fast rules about it's use.  His guidelines were that the stuff flashed off so fast that it was okay to put in your mouth after 24 hours. 

Mark