Why not add catalyst after Q-cells?

[MrMik]

I just stuffed up the second lot of resin/catalyst/Q-cell mix and don't have much left to get a ding repaired
I used 75ml resin and 0.75ml catalyst at 27degC and added the catalyst (as per instructions) to the resin before adding the Q-cells.
Then I started adding in the Q-cells and it took me 8 minutes to get the consistency right and smooth out remaining lumps. Just as I was ready to pour the mix, it started to gel and set in the pot
<:

I cannot see any good reason why I should not mix the resin and Q-cells leisurely until it is perfect, and then add the catalyst and mix it well for 3-4 min.
That would leave me 4-5 min to pour the mix into the ding and work out air bubbles before it sets.

Why do the instructions say to mix the catalyst in first? Is there a reason or do they just want to sell more resin when people like me stuff it up?

[ric_vidal]

Not sure where it says that order, MM, I never did. Do it however you like, and you certainly don't have to mix for that long. Just make sure it is MIXED well enough.

Also, keep in mind resin in volume gets hotter, so if you have a deep hole you either have to build up in stages (multiple mixes) or use less catalyst. If it starts getting too hot you can always put a wet cloth or sponge over it to cool it. You can always back-fill the cracks even with UV resin and a small amount of q-cell.

Many, and I mean many, a fill of resin/q-cell cracks due to heat. It is not really a problem, it's just being used as a filler, it is the glass over the top that is important and gives the ding the integrity.

You can also use water-based fillers to do the same job – 'microfibre' is a very light, white, water-based product used by hobbyists, it can be used directly on blanks and to fix dings, same as above though, has to be glassed over.

[MrMik]

Thank you very much, Ric_Vidal!

I thought that I'd get an email to announce replies, but got no email. I only found your reply today. Otherwise I would have replied earlier.

I managed to mix another batch of Q-cell-resin-mix and pour it in before it started to set. I got a lot faster (or less obsessive about mixing )

That was followed by numerous layers of fibreglass and UV resin, until I got it right.

The good news is that I cannot feel the ding repair with my hands. But the Q-cell is definitively not the same white as the rest of the board, it looks like a grey patch from most angles. Never mind, less risk of the board getting stolen that way.

The really good news is that the board and myself seem to have done some "bonding" during the (lengthy!) repair efforts, and now the board works for me! We're a team now....

[ric_vidal]

But the Q-cell is definitively not the same white as the rest of the board, it looks like a grey patch from most angles.

Never will match MM, they are literally two different things. If you want it too 'look' better you can give it a dusting of paint, but ultimately even that will look different as the foam yellows with age.