OK. I have found the problem.....
Hands up all those who said it's coming out of the floor and go to the top of the class...
Here is what I have done...
I took half a 25bag and carefully poured it into 3L of water, mixing as it was being poured, a little at a time. No SBR - just water. And taking great care that there was no contamination :-).
I had in the back of my mind John Armstrongs post (above) about making sure the floor was wet... Well I overdid it a bit and put a bit too much water down. The mixture when laid on this was without doubt a bit too runny. Anyway - same problem - bubbles. However there did seem to be slightly less, and it did seem to respond better to the roller. When dry there were marginally less bubbles than my earlier attempts.
I then did the same but this time with SBR/Water mixture. But less water on the floor. Same old problem - bubbles. However this time it was a little thicker and rolling did not help.
Now I'm thinking to myself that I have not done a very controlled test - and how am I going to explain it to the NG. In fact I was feeling ticked.
I have the floor divided into three and there was one more bagfulls worth to finish off this section. I decided to lay this last bagfull - and decided to make it a little looser and with lots of water on the floor first. So I put plenty of water on the floor, swept it all over and got on with the mixing.
When I finished mixing I applied a bit more water, and sat down for a moment waiting for the mixture to stand. As I sat there I caught some movement on the wet floor where the light was shining. I could also hear some very soft clicking noises. On closer inspection I found that the whole damn floor was "leaking" like crazy.... Blowing bubbles through the water! Not just the odd bubble here and there - great long fizzes of the stuff!
So I left it for a bit and the clicking and fizzing slowly subsided, then added water and the bubbles started again but slightly less. I repeated this for about 20mins but the bubbles kept coming. I had to lay the mixture before it went off and sure enough the bubbles appeared as usual.
OK - so now we know where it's coming from - how do I stop it. PVA Sealer? Well that didn't work on the StoreRoom floor that I did earlier. I put a 3/1 PVA Mixture on that and it still produced bubbles... Hmmm...
Thoughts?
Roy