Catalyzed Poyester discoloration?

[gerberguitars]

For those of you who have used a catalyzed Polyester on acoustic guitars....have you noticed any discoloration from the catalyst reacting with the polyester? The guys at Simtech say that their product is superior in this regard and that it's barely noticeable, but still there. To what extent has this been an issue for you?

[Tim McKnight]

The discoloration is from the addition of one of the two catalyzing chemicals, Cobalt. In its liquid form, Cobalt is dark blue and when added to polyester it adds a slight hint of a bluish / green coloration to the finish. However, when you add the second catalyzing chemical, MEKP, the hue turns more of a yellowish / green color. Not to fear though, when the finish material is atomized and sprayed on the instrument the color is unseen and does not impart any color value change that is visible to the naked eye. If they [Simtech] are touting any color value benefits of their product, then its possible they are using different chemicals to catalyze the polyester or perhaps using a lower / reduced percentage of Cobalt.

I should also note that I have not personally seen any color changes, over time, due to UV interactions.

[Brackett Instruments]

The normal amount of cobalt required is 1%, at least with the few brands of Polyester I've used. It does turn blue when added, and then kinda brown after the MEKP is added..............however it's a clear as any finish I know of after it's applied to an instrument. I can't see any tint in these pictures.

[gerberguitars]

Thanks for the pics of the Bracket guitars...looks great!