Clear film on top of bio?

[Tony]

Odd this one.  This is bio that has settled for a while.  I'm experimenting with gentle bubbling just to "turn it over" to see if it helps remove the last traces of soap by bumping the molecules together, as an alternative to pump agitation:

http://youtu.be/gCZ-iuVvlok

[Dickjotec]

I bubble at about that rate but have never had a film like that. It looks waxy? Does it clump up when the bubbles start? Can you lift it out with a sieve or similar? What does it feel like?

[Julian]

I've had very thin patches of "scum" on bio before.  Not that white and not while bubbling. 

Interesting.

[Tony]

Not a skin as such and no clumping.  When I'm bubbling to demeth it's a violent bubble, this is just a trickle to keep things moving. The violent bubble does sometimes lead to scum and clumping, but that's not what seems to be happening here.

[kamaangir]

Watched the vid and am puzzled. Did you do anything different on that batch?

[Tony]

No, I've seen this before with other batches.  It may just be an oxidised layer or layer formed by dust that sits on top?

[greasemonkey]

It looks to have rainbow colours in it.
Could it be some kind of oil or grease? Oil seal failing in a pump, or not even failing, just allowing a tiny bit of grease out of the bearing?
Dunno why you breath turns it white though. What you been drinking?

[Tony]

It looks to have rainbow colours in it.
Could it be some kind of oil or grease? Oil seal failing in a pump, or not even failing, just allowing a tiny bit of grease out of the bearing?
Dunno why you breath turns it white though. What you been drinking?

I guess normally we see rainbow colours with oil drops on wet surfaces, where the oil spreads out to be a few molecules thick.

In my case we have an oil of sorts, and water from my breath.  Perhaps the same works in reverse and it's the water in my breath that forms a layer of molecules.

The white stuff, perhaps that is an emulsion with the water?

I don't think it would be caused by another oil, IE grease, because that would surely just mix in?


Arash no this is the same as many batches, I've seen this type of effect before too.

[greasemonkey]

Just hypothesising, coz I don't know much about it, but what if there was a layer of moisture on top of the bio, due to high humidity in the air? It would explain the intermittent nature of it. The tiny traces of oil would then be floating on the moisture? Or would any moisture just sink in the bio?
That white stuff does seem odd, but then I guess all sorts of things can happen at a molecular level, given how many different chemicals and whatnot is involved.

[kamaangir]

Well the rainbow effect is usually water refracting light differently. 

[nigelb]

Never seen anything like that before. Probably just another side issue with the method you employ.

Never seen that with water washing!

[Tony]

Maybe it doesn't form if the bio contains some moisture?  Certainly it shows a reaction with just the tiny amount of moisture in my breath - my bio is extremely dry having never been washed.  Water washing may leave a level of moisture in the bio and perhaps any effect gets washed out.

That said, I don't think it's related to process.  I suspect any bio left open to air for a week then bubbled like this may exhibit it if it's related to surface oxidisation.

It's bit of a non-issue, more of a curiousity than anything else.

[nigelb]

It's bit of a non-issue, more of a curiousity than anything else.

...Aye...it is one of the strangest things (bio related) I've seen for a while!

[Tony]

New information - the batch I finished last night has bubbled 10 hours vigorously overnight.  This morning I have switched to gentle agitation on the bubbler and it had exactly the same effect - a boundary is visible.  I guess I've just never noticed before.  It is pretty subtle.