Urgent boiling advice needed

[randomseeker]

I started up my evaporator today and things were going according to Hoyle when I began to hear banging from the pans. The sap level was below the top of the flutes by several inches. I flooded the pan, made the adjustment for the going forward feeding, but I have a lot of burnt sap in the sap pan, much of it like ash, very black. I scraped what I could out, but there is still more in there. Also, when I fired up again (with the blower), it boiled over right away. It seems to be behaving with no blower going, but it is an airtight box with only the air moving through the idle fan feeding it.

The pan, thankfully, looks fine. No apparent damage or leaking.

1. Any ideas how to treat the sap so that it doesn't boil over so viciously?
2. Should I abort, drain and clean the sap pan and start again?
3. If not, can I expect a burnt flavor in the syrup?

Thanks all.

[DaveB]

First off, everyone does this or has had this happen. You did the right thing by flooding the pan but you should have a five gallon bucket full of sap ready to go for just such emergencies. It's one of the things that I always make sure I have before firing up.

I would wash the pans because I think the burnt sugars can lead to off flavor in the syrup and it also reduces surface area so you you won't get as good a boil. It can also lead to hot spots which could warp the metal. Just my 2 cents.

[OGDENS SUGAR BUSH]

Should I abort, drain and clean the sap pan and start again?
3. If not, can I expect a burnt flavor in the syrup?
yes and yes

[Marcus]

I burnt a pan last year, kept boiling what sap i had left which wasn't much. It had a burnt flavor. I would not throw it away unless it is to bad. I am using my burnt syrup in my cereal. I did have to shut down and spent the next day and half cleaning with vinegar and plastic scrapers and plastic scrubbers. Vinegar is year friend.

[RollinsOrchards]

What are you using for defoamer?

I have taken to hanging a cup of powdered defoamer above the flues, so that when we do get a runaway foam-up that it will hit that powder and should even itself out. Not foolproof by any means.

[Urban Sugarmaker]

My first season I had this exact thump/bang noise. It's the sap trying to boil through thick niter build-up. Bubbles are forming under the sugar sand and "exploding". Now that I boil RO concentrate, it happens much sooner. As long as I reverse the flow every boil I don't get this issue. With your setup you are producing syrup and niter quickly, so this does not surprise me.

When this first happened to me I freaked out and shut down thinking that fire bricks were exploding.

I would say as soon you start hearing this noise it's time to reverse flow or clean the niter out. I will never upgrade to an evaporator that doesn't have a same-side reverse option that can be activated mid-boil. It's a must have for me because the trees I tap produce a lot of niter.

By the way, I had a small scorch of burnt niter due to this, so I suspect that's what happened to you.