Draw Off Channel Foam

[n8hutch]

So last night was my 5th boil on my 2.5 x8 evaporator, it has a reversable cross flow pan, about half way through my boil I started to get a constant Foam in my Channel that I am drawing off, running at 1-1/2 inches. I measured the foam at like 2-1/4 inches, It doesn't get any higher than that but no amount of defoamer will knock it down.
The only reason it concerns me is I know it can throw off my thermometer in that channel. I am thinking I just had a real hot fire & that was what caused the foam, I was drawing off syrup about every 15 min but the foam would not receed . any ideas?

[tstew]

My guess without knowing any of the details but it might be sugar sand starting to build on bottom of your pan. My evaporator does the same thing after boiling for a while but mine is caused by sugar sand. Once done with that batch I drain off the syrup pan and clean it and it goes back to normal until the niter starts to build agian.

[northwoods_forestry]

My draw off channel foams up all the time. Unless it is climbing over the pan dividers I don't worry about it. If it does get over the dividers I add defoamer right at the takeoff.

[PerryW]

hmmm, never seen any foam that wouldn't disappear w/ defoamer. Maybe TSTEW is onto something with the nitre buildup. Are you reversing the flow each time? (for the record, I reverse my flow with each boil, but never actually clean the pan unless I make significantly more than 100 gallons of syrup.

[mellondome]

Is it foam or just the boil breaking higher... that is a lot of syrup for a bubble to raise through.

[n8hutch]

Yeah I reverse the flow every boil, I have cleaned the syrup pan once already. It worked fine It was just kind of all of a sudden it appeared. I'll see what it does in the opposite direction tonight.

[n8hutch]

Pretty sure it is niter build up on the bottom of the pan, going to give it a good cleaning tomorrow.

[village idiot]

do you mean bubble foam or that scum type of foam?

Bubbles I ignore (I do de-foam the back pan consistently), scum I strain off because it looks gross.

[n8hutch]

Yeah its bubble foam, I am not supper concerned about it. When I reversed the flow last boil it went away for awhile & then showed up in the New Draw off channel, I think it would be OK but decided to clean the pan anyway.

[RileySugarbush]

When we get this it is always niter on the bottom of the pan near the draw off. We check for niter while boiling by tapping the bottom of the pan with a scoop. Center channel, no niter, sounds tinny. In the drawoff channel it will sound soft and muffled. Time to reverse flow.

It is not unusual for us to reverse flow two or three times during a session.