Possible other causes of pinholes

After doing a resin flooring project that should have had pinhole issues and didn't, I started to question why. Perhaps we've dismissed the most important parameter?

We are used to the theory of applying coatings on the cooling cycle of concrete, with the idea being that the air is cooling and therefore shrinking back into the voids and drawing in the resin.

I thought I'd discuss the various points noted on this job so that we could include some industry experts into the conversation for comment. I raise one particular climatic parameter that we never seem to discuss as a possible contributor.
Hopefully we can gain some good input and better understand one of the most painful problems in resin flooring.

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Jd Grafton
Jd Grafton wrote:
6 May '20 12:31am
Interesting observation.

One would surmise that if there were pressure trapped within the concrete, that a falling barometer would allow the trapped pressure out of the slab.

Humidity, temperature, preparation, application, mixing, timing, surface profile, equipment, and applicator technique.... It's actually quite remarkable we can ever get a good coating.

For this project perhaps you should look at the type of underslab vapor retarder and the temperature delta during the installation and cure phaze. And if you ever are able to replicate this type of performance - buy a lotto ticket immediately!!
Resin Jack
Resin Jack replied with:
8 May '20 6:43am
Thanks for the comment JD,

I totally agree, when you consider all the factors that comes into play that can cause pinholes, it does make you wonder we ever get a satisfactory result. I guess that is what made me start to question my assumptions. I do have a record of climatic conditions during installation but I don't have a record of climatic conditions during the overnight cure. There is no doubt the temperature would have dropped overnight but the resin would have been gelling whilst the temp was still increasing, so the pinholes should have been there if it was only to do with temp.

This slab does have a plastic sheet but no other forms of moisture vapour barriers were installed.

Thanks again. Keep smiling @resinjack
Kevin Reusch wrote:
29 Apr '20 10:35pm
Jack, while atmospheric conditions certainly have an effect on coatings during application and cure I have seen pinholes arise in controlled environments as well. There are some many variables that can play in to this but application methods and existing conditions, in my opinion, play the biggest roles. It is obvious you understand this so I’m curious as to your testing of the existing space, what means and methods do you use, and what application techniques do you use for you coatings, squeegee bankroll or simple dunk and roll?? Regards.
Resin Jack replied with:
1 May '20 8:25am
Hi Kevin, Thank you for your comment. There are actually a number of videos of the installation that will appear in future posts. I agree that pinholes can appear in controlled conditions but in this video I discussed how, in theory, I should have had pinholes but I didn't. I would like to credit product, good application, etc etc but it was the lack of pinholes that really started to question if there was something else that I was overlooking. FYI This floor was a solventless rollcoat applied direct to concrete using squeegee and wet back roll. Again thank you for you comment. It is always appreciated.

Take Care and keep smiling

Adam Haining wrote:
28 Apr '20 6:06am
I know in terms of moisture vapor transmission, as the isobars widen, the transmission rate increases because a wet substrate is trying to dry out and equalise the pressure.
Resin Jack
Resin Jack replied with:
29 Apr '20 1:03am
Thanks for your comment Adam. So in this case with a storm coming, do I take it the vapour transmission rate would be decreasing?