Analog board: White residue -> disintegrated protection coat?

[retrofreak83]

Hello all,

I recently had some small solder work on a SE/30's analog board.
I used (no-clean) flux. Afterwards, I noticed some greyish/white residue/shimmer on the board. I cleaned the spot I've been working on using isopropyl alcohol. I got the impression that like the more I used it (on the greater area), the more shimmer came up.
After all, the areas that I have used isopropyl alcohol on seem to be cleaner (see image with "cleaned area" text) and also feel smooth:


There are also areas which not been touched by me so far but look dull. It also feels dull.



So what I'm asking myself is:
Were these boards equipped with some kind of protective paint?
Is there anything that needs to be done here? In particular, I can't get the solder joint any cleaner than it is.

 

[Iesca]

Isopropyl can leave a white powdery film. I wipe it away with a clean paper towel or similar.

 

[Phipli]

What %age is your IPA?

 

[LaPorta]

99

 

[Byrd]

It's the thin resin coating on the PCB that reacts to the IPA being applied, if unsightly I find a squirt of electronic solvent cleaner + lube (some don't have the lube check this!), removes the white mar and makes it look like new.

 

[retrofreak83]

What %age is your IPA?

99,9%.