Tony, I seem to remember having a conversation with you about this foam on top,
didn't we decide it was due to not demething completely.
It seems (though it's hard to tell) that there is a correlation between the amount of Methanol remaining and the time taken for this foam to appear when bubbling. So if I have a really well WBD'd batch it can appear in less than 24h, but otherwise it can take a couple of days of bubbling.
My feeling was that the foam appearing indicated that very little Methanol remained in the batch, so I bubble until I see it these days.
I suppose I should see if the foam is soluble in Methanol. I anticipate that it will be, certainly from conversations here it appears to be one and the same with the HMPE (or whatever it is) cream that forms at the bottom of batches. Usually I stir the foam into the surface and it sinks (to become "HMPE"s?)
Certainly from my reprocess batch the creamy stuff gives a 3/27 pass - soluble in Methanol - so if the foam is the same it will also be soluble in Methanol - which ties in with my speculation that it doesn't start to appear until the Methanol has been driven out.
My bubblier was always in the very bottom, I'd have to pull it out of the settled soap/gly each time I did a new batch,
and then let it rest on top.
I've only ever seen honeycomb looking stuff form on top, and this was if I'd made a really soapy batch.
My bubbler is also resting on the last batches drop out and I never get a head like that in the picture. I did in the very early days of bio brewing but not for years now.
Just to add to this part of the debate, I've done an overdose batch (bone dry oil and excess catalyst) and got a single stage sparkling clear pass on the 5/45. Went on to do WBD up to 90C. Bubbled from 1/3 up from bottom of the settle drum this time, but still got a creamy/foamy top. So I don't think it is necessarily stirring up soaps from the bottom that causes it.
Was Acetone added to this batch ?
No acetone in that one, no.