Polyester Repair

[Sy Zabrocki]

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Who out there has had experience in polyester repair? 

My main question is: What is the usual ratio of hardener mixed with the polyester?

An older instruction sheet from Kawai suggests 5 drops hardener to one teaspoon (5 milligrams) of polyester. That has worked for me on several small pours. I usually insert a hammer shank in the bottle, withdraw the shank and dispense one drop at a time. The problem is some drops are noticeably larger than others. There are these anxious moments on each pour. You only have a few minutes to work because the mixture starts to jel and harden. 

If there is not enough hardener the mixture won't harden completely. Some heat is produced from the reaction when the two mix. Too much hardener on a larger pour could cause too much heat and maybe other problems.

Suppose you were going to do a larger job with a pour of about 6 teaspoons. This would require 30 drops of hardener. Applying 30 drops with the shank method might be to slow. Some of the mix would already be starting to harden by the time the 30 drops were dispensed. As stated above you only have a few minutes to work so there are anxious moments. 

Is there some other ratio besides "drops" that would apply to a larger pour? The next best  way would be an eye dropper or a needle nose bottle. 

I have not used the German Konig kit but do have their manual. Their hardener comes in a tube and is applied in a bead from the tube. The length of the bead is equal to the depth of poly in the container. 

There is enough anxiety with the whole job anyway you look at it. I only do this work out of necessity because we sell pianos. 

So, can anyone tell us more about the ratio of hardener? Is it pretty much the same with the various piano makers?

Sy Zabrocki