When is niter in danger of burning?

[mol1jb]

Heres the situation. It is late season here in central IL. Getting more niter build up in the last channel of the syrup pan. After we finish the boil I can see it is medium brown and sticking to the pan. It comes off with water and a green scotch scrubber fairly easily.

My question is am I close to burning niter with this build up developing?

[Galena]

*scratching head* Though nitre is potassium nitrate - and in fact an ingredient in gunpowder - I honestly don't think it can burn. I've had buildup like you describe and yes it comes off easily and will also chip and flake off readily when dry. But ignitable? Good question for Dr Tim Perkins, our resident international expert on all things sugar :-)

[ecolbeck]

There appears to be several definitions of niter. The one used in the sugaring context is most definitely not related to gunpowder. It is a calcium salt of malic acid which is an organic byproduct of tree metabolism. Niter will burn in the sense that toast will darken and burn but not in a combustion sense. Hopefully a more experienced sugar maker can chime in to answer the OPs question about when niter accumulation becomes critical.

[Russell Lampron]

Any time that nitre starts sticking to the surface of the pan it can burn. If the build up is bad enough you can scorch your pan, especially when drawing off.

[mol1jb]

Any time that nitre starts sticking to the surface of the pan it can burn. If the build up is bad enough you can scorch your pan, especially when drawing off.

You say when drawing off because the pan level drops a bit? Would reversing flow half way through a boil help reduce this? I currently just stay on one side draw because I only boil 4-6 hours at a time, thanks to RO, but late season I may have to modify to deal with increased niter.

[Russell Lampron]

You say when drawing off because the pan level drops a bit? Would reversing flow half way through a boil help reduce this? I currently just stay on one side draw because I only boil 4-6 hours at a time, thanks to RO, but late season I may have to modify to deal with increased niter.

Change the side that you draw off from each time that you boil and you should be all set. I have two front pans for my evaporator and swap them out at mid season or after making about 100 gallons. I boil 14% concentrate and am planning to go higher now that I've upgraded my RO. I also have an air injector which helps with keeping the nitre build up in check.

[mol1jb]

Change the side that you draw off from each time that you boil and you should be all set. I have two front pans for my evaporator and swap them out at mid season or after making about 100 gallons. I boil 14% concentrate and am planning to go higher now that I've upgraded my RO. I also have an air injector which helps with keeping the nitre build up in check.

I should also say that I drain and clean my pans after every boil as I only boil every other day.

[Galena]

There appears to be several definitions of niter. The one used in the sugaring context is most definitely not related to gunpowder. It is a calcium salt of malic acid which is an organic byproduct of tree metabolism. Niter will burn in the sense that toast will darken and burn but not in a combustion sense....

Awww dang! So what am I going to blow things up with now? ;-) JKING

[DrTimPerkins]

Niter, as used in maple production, describes the substance that precipitates onto pan surfaces. More technically this is termed "scale" niter. Some of this scale will break off and form small chunks, which are referred to as "sugar sand." It's all pretty much the same thing, although there are differences in composition and nature from the entry point of the evaporator to the drawoff and during a boil and over the season. In general niter is mostly composed of calcium malate, which results from natural minerals and organic acids in sap.

When the build-up of scale becomes excessive, heat transfer into the syrup is retarded and evaporator efficiency declines. Worse still, because there is no liquid under the scale, the pan can overheat, scorching the niter and any sap/syrup entrained in the area. In severe cases this can cause serious warping of the pan. Overall, excessive niter build-up is to be avoided. Scorch or burnt-niter off-flavors are very difficult to blend out, so typically the syrup is ruined.

Excess niter occurs during long boils. Unfortunately determining the point of incipient problems during boiling is difficult. It's kind of like driving towards a cliff in the dark. You know it's out there, how close do you want to be before you turn away? Some people take action early, some less frequently, and some too late. One way is to watch the boil. Very tiny fine bubbles, often very light-colored, will appear when niter is getting thick. You can also feel it by rubbing a scoop across the bottom of the pan lightly A good reliable indicator is mostly found through experience...sometimes not good experience.

The temporary solution is to reverse flow periodically during boils. The timing depends on several factors, but typically every 1.5-2 hrs. The long-term solution is to clean your pans frequently. Generally you need to do both (short-term reverse flow, long-term cleaning). Some years, or in different parts of the season you might be able to do 3-4 hrs before switching sides....other years of parts of seasons you might find yourself switching sides every 45 minutes. Difficult to give any hard and fast rules. The one useful piece of advice might be that if you think it's time to switch sides...it probably is. Once you develop the proper method for your evaporator, it's not real difficult, although it might result in a rather large drawoff shortly afterward before settling back down.

[berkshires]

Thanks, as always, for your willingness to share your knowledge, Dr Tim!

I just batch boil for a number of reasons, but may at some point get a divided pan. So one thing I've never understood, and I'll ask, since it may be helpful for others:



The temporary solution is to reverse flow periodically during boils. The timing depends on several factors, but typically every 1.5-2 hrs.

I thought it can take a full long boil session to establish a gradient. Then at some point in the next boil you can start drawing off syrup. So then if you reverse your pan every 1.5 - 2 hrs, aren't you reversing your gradient each time? How do you ever wind up with syrup in the end of the last channel? I must be missing something. Seems like you'd just wind up with your whole syrup pan eventually turning to syrup, and then you'd have a big problem!

Can anyone help explain?

Thanks!

Gabe O

[DrTimPerkins]

When you're sweeting the pans (first boil), you probably wouldn't need to switch sides.

After that, the typical procedure is that when you're ready to switch sides, you:
1) let the fire die down a bit,
2) draw off some syrup/near syrup (amount depends upon size of evaporator) from the current draw-off location.
3) pour the syrup/near syrup into the final partition of the new draw-off location.
4) bring the fire back up.
5) start drawing syrup off a little at a time while still a little lite in density. If needed, add a little sap to the early-mid partitions to thin out.
6) be prepared for a big drawoff at some point in time. With our previous 3'x10' running 15 brix concentrate, this could amount to about 5-gal or more of syrup. With our 4'x12' (8' of which is flat pan) and high-brix concentrate, we might get a 30-45 gal drawoff, about half of which is pretty high density (225+ deg F syrup) and need to thin it out with concentrate. That can get a bit exciting at times.

Yes, you are correct that you can sometimes end up with an entire flat pan of syrup if you don't do it just right. Have the oh sh** bucket of sap close by and make sure you're floats are working (not clogged) and you have plenty of sap/concentrate in the head/feed tank.

Often, after step #3, you might adjust the floats a bit deeper for a little while to allow more fluid to be drawn into the flat pan to thin out the back partitions. Depends on what you're running (sap, concentrate, high-brix concentrate) and the size of the evaporator.

The exact procedure will vary depending on several factors.

[berkshires]

Okay, that all makes perfect sense. Wow, that's a lot of machinations to go through every hour and a half! And seems really easy to suddenly not be able to draw off fast enough, or have syrup in your middle channel! But I guess once you get the routine dialed on your evaporator, you can do it with your eyes closed.

On a little hobby-sized evaporator (like 2 x 4 and smaller) I have read that it not so necessary to switch sides and/or empty and clean your pan as often. That is encouraging, if true! Before posting my question I was searching on this site for how this might work, and I ran into someone who said he had a reversible pan, but had never switched directions in all the years he'd been boiling! He said he just drained and cleaned the syrup pan once or twice during the whole season.

Thanks again!

GO