Is it a bad idea to use one manufacturer's product mixed with another - or is it all pretty much comparable within the same paint type (Urethane in this case)?

I have purchased a pint of the R-M Diamont Base and Clear Coat with their UR reducer. I'm doing a small repair (3ft x 10ft) on my motor home to repair peeling clear coat above the windshield.

The product sheet for the Diamont Base says I can add 10% hardener (BCH2) - which I read here is a "good idea" but not totally necessary.

I would like to do this but I can't find the BCH2 in anything less than a quart for $125. I only need about an ounce. Lookign for the BCH2 I see other brands of urethane hardener (smaller quantities).

Is it safe to mix another brand (like this ... https://www.amazon.com/dp/B00397TVJC/re ... B07BFBWSZK )

Is it a bad idea to use this (should I just skip the hardener in the Base coat)?

EDIT: I'm not going to use the product I linked to above.

use the hardener you have for the clear, that should work

also i would only do 5%

10% is to much IMO

Thanks. I did not think of that.
The Clear Coat I'm using is the R-M Diamont DC01NB Speed Clear. https://www.coatingsmall.com/cap_data_d ... dc01NB.pdf

I have the DH18 (slow) hardener.

This is the Base coat https://www.coatingsmall.com/cap_data_d ... amonts.pdf

I wonder why R-M recommends the BCH2 hardener. What's the difference between the DH18 and the BCH2? Maybe I can figure it out from the MSD sheets.

I called R-M Tech Support and asked them if it is okay to use the DH18 in place of the BCH2, and they said it is fine if I'm doing an interior panel, but it would be better to not use a hardener if its an exterior panel (which mine is) if I can not get the BCH2.

I did not get into the specifics of how these products differ - however I will take their advise and not use the DH18.

I should have called them in the first place but did not consider using the DH. It was a good thought though. I know they would not have recommend that "other brand" hardener I linked to earlier.

There is a website "Finish Master" that sells the BCH2 in an 8oz bottle - but so far I have not been approved to buy anything from them. I don't know if they sell retail.

the idea is that the hardener in the basecoat will cross link with the urethane sealer and the clear will crosslink with the basecoat,

chip resistant, durable, and just a better paint job.

do as you wish but i still recommend 5% hardener in that basecoat, same hardener thats in the clear

sometimes you have to read between the lines. paint company's really don't want to advise you to do anything outside of the normal. sometimes us chemist know better, I also would use the clear catalyst.
Jay D.