Sweetening the pans

[Smeds]

I'm going from a homemade arch with 2x4 flat pan to a forced air Smokey Lake Corsair arch with a 2x4 divided pan this coming spring. I know this subject has been repeatedly covered, and the search function helped me a bunch ... but one thing I could NOT find an answer to was this question (forgive me in advance, maybe I didn't look hard enough):

I know it's going to take a good amount of sap to sweeten the pans (likely 150 gallons or more) until I can start drawing off ... but is that initial sap just "lost" to the sweetening process, or do you make it up eventually? For example (assuming 40:1), if I end up boiling 400 gallons of sap overall, will I still end up with 10 gallons of syrup? Or will I end up with about 6.25 gallons? I saw a post that said that once you start drawing off, you pretty much hit that 40:1 ratio for the rest of the sap. If that's true, then the first "sweetenings" must be lost to the process? If they're not lost, then after the sweetening the ratio should drop ... right?


Thanks all ... excited to see what this new arch can do. I was squeezing about 11 GPH out of my old flat pan arch with a homemade AUF setup, wrist-sized pieces of red oak, and firing every 8 minutes. From what I've read, if I do the same with this new arch I can possible see 15-16 GPH. I've also moved inside of a new pole barn, so installed a hood with their 10/14 Concentric Exhaust system. Drafts really well already, the blower fan slowly spins by itself most days.

[DrTimPerkins]

You will definitely enjoy moving to the divided pans. Smokey Lake makes a nice product. My brother-in-law just got a SL arch for his rig.

The syrup is "tied up" in the pans for the duration of the season (unless you "boil out" at some point along the way), but you will reclaim it at the end when you eventually boil out the pans. The trick is making sure the pans don't go ropey or spoil during warm spells. To do that, make sure you DO NOT add any UNBOILED sap at the end of each boil, and that during any intervening periods when it is warm but the sap isn't running you start a small fire in the rig to bring the sweet to a boil for 5-10 min every 2-3 days. This will keep microbes from spoiling what is in the pans. Alternatively you can "boil out" every now and then, but that means you'll need to re-sweeten the pans again the next time you boil.

[Super Sapper]

When sweetening the pan you are increasing the sugar content in the pan to a point where there is syrup at the draw off. It is not a consistent density across the pan but goes from whatever your sap is to syrup at the other end. This sugar "captured" in the pan will be recovered when you boil this down at the end of the year or whenever you need to empty your pan.

[Openwater]

Is there any kind of formula out there that can be used to predict how much sap it would take to sweeten a pan at a specific pan depth? Obviously, the variables in the formula would be volume of sap/syrup in the pan at a constant depth (say 1"), sap sugar content and desired draw off syrup concentration/brix.
Also, once the pan is sweetened and you run out of sap during a boil, could you just draw off what's left in the pans, refrigerate it and put it back into the pan when you get enough sap to boil again? Or is the intermittent firing/boiling preferred during warm/"dry" spells? I assume the pan gradient is lost as soon as the sap in the pan cools.
Thanks for the answers and info. I'm getting prepared to switch to a divided pan next season.

[Pdiamond]

You will lose the gradient as the pan cools with a divided pan. It does come back quickly the next time you fire provided you use the liquid you have in the pan or maybe stored because of warm temperatures. At the end of the season when I had a divided pan and ran out of sap I used water to push thru the sweet as much as possible. My SL 2 x 4 with AUF and a raised flue pan does between 40 and 50 gallons an hour when it is really roaring. You are going to really like the new evaporator and being inside with it.

[berkshires]

Is there any kind of formula out there that can be used to predict how much sap it would take to sweeten a pan at a specific pan depth?

Theoretically it is the amount of sap required to make an even gradient in which it is syrup on one end and sap on the other, which is to say that it is on average 33% sugar. So if you calculate the volume of sap it would take, given the area and depth, to boil down to 33% in an undivided flat pan, that should get you in the ballpark.

In practice, I think it's a bit more complicated, because of mixing within channels.

That said, in my 2x3 last year (my first year on a divided pan) it took me only about 40 gallons to get to my first draw. I was pleasantly surprised. I think I was running at a little under an inch deep.

Gabe

[DrTimPerkins]

I think I was running at a little under an inch deep.

While as suggested, experienced operators can run their pans quite shallow, since this is a new evaporator and new process (divided pans) for you, I'd suggest boiling deeper than that. Maybe start with 2" (or even more). Then as you gain experience, drop the level a bit each boil until you get to a point you like. The boil won't be quite as hard if it's deeper, but it'll give you some margin for error. Kind of depends upon how attentive you are also. With 2", you might get a chance to hit the bathroom (if nearby) occasionally if you're quick about it. If your level is under 1", don't step away from the pans unless somebody else (who knows what to look for) is there watching it.

I have never understood the concept and practice of filling the pans up and then walking away to do other chores while it simmers. Seems like a recipe for disaster, and it not infrequently ends up that way. There is a fair amount of water to boil off going from 40 to 66 Brix, but only a very small amount going from 60 to 66 Brix. The amount of water to be boiled off as Brix increases is not linear, but exponential. Boiling is kind of like a sled starting off on a low slope going slowly downhill. The slope gets steeper and steeper (the Brix gets higher and higher) as you go down. The problem is that there is a wall at the bottom (burned pans). As you get further down the slope (higher in Brix), you speed increases (the proportion of water boiled off), and keeps going faster and faster. So you need to be there to stop the sled, before you hit the wall -- which is no fun at all and can be quite expensive.

[Openwater]

That said, in my 2x3 last year (my first year on a divided pan) it took me only about 50 gallons to get to my first draw

Gabe, was the 50 gallons raw sap (2-3%), or was it RO'ed down from a larger volume?

[berkshires]

Gabe, was the 50 gallons raw sap (2-3%), or was it RO'ed down from a larger volume?

I checked my notes this morning, and I think it was more like 40 gallons. 35 Gallons went into the pan on the first boil, and then my first draw was 45 minutes into the second boil.

Straight sap, no RO. I measured it at 2% for that first boil, and 2.1% for the second boil.

And for whatever it's worth, my 2 x 3 has four channels. I'm not familiar with the SL pan, but presumably it has four channels also? If it has only 3, I would imagine it would probably take more sap for a given depth to get to the first draw, since a larger volume is mixing in that last channel. But I'm no expert!

GO

[Smeds]

Thanks folks ... good information. Sounds like eventually, you end up with the normal ratio of sap to syrup ... which is what I thought. A few old posts I read led to some confusion on my part. Always good to confirm with those that have more years of experience!

I'm looking forwards to seeing that Concentric exhaust work, being inside and not being a slave to the weather for boiling anymore!

[Swingpure]

This will be first year with a divided pan and I have read lots on this site about it. I accept that it will take 150 gallons of raw sap to sweeten the 2x4, 4 channel pan. But I need to understand it.

If I just had a flat pan and boiled 80 gallons of sap, by the end of the day, I would have 2 gallons of syrup. I understand the principle of the gradient, but if I boiled the same 80 gallons of sap in a divided pan, for basically the same period of time, at the same level, wouldn’t most of it also have turned to syrup?

I will be boiling everyday I have sap to boil. I thought I read someone suggest to plug the openings at the end of the runs overnight to help keep the gradient. When I asked my pan maker about that, it was the first he had ever heard of that. Is plugging the ends overnight a common practice?

[Pdiamond]

When I had a divided pan, I never did that. I would just shut down for the night and put extra sap into the pan so it would not boil out or make syrup while unattended. Mind you the fire was out completely but the firebrick was still hot and would still evaporate an additional 1/2" of liquid. There is a little mixing overnight, but when you fire up the next day the gradient reforms rather quickly. You'll get it figured out after your first couple of boils.

[DRoseum]

I would recommend plugging each channel divider port to keep your gradient as much as possible. Also for reversing flow the plugs are also useful, so you can pull it off into separate buckets/pots for each channel and put it back in and limit intermixing.

If your channel ports are round, you can easily make plugs out of high temperature silicone stoppers. I made stainless handles that I bolted to the stoppers with a small stainless bolt with washers on each side. Works great and keeps it all divided.

Doing this helps maintain lighter grade syrup on subsequent boils.

[bigschuss]

If I just had a flat pan and boiled 80 gallons of sap, by the end of the day, I would have 2 gallons of syrup. I understand the principle of the gradient, but if I boiled the same 80 gallons of sap in a divided pan, for basically the same period of time, at the same level, wouldn’t most of it also have turned to syrup?

I will be boiling everyday I have sap to boil. I thought I read someone suggest to plug the openings at the end of the runs overnight to help keep the gradient. When I asked my pan maker about that, it was the first he had ever heard of that. Is plugging the ends overnight a common practice?

Yes, boiling 80 gallons of sap in a flat pan or a divided pan at the end of the day will give you 2 gallons of syrup. But in a 2x4 pan that 2 gallons of syrup might be like 1/4" or so. You would never bring the level down that low unless you like living on the edge. The idea of consuming 150 gallons or so in a 2x4 pan to sweeten it is that you can maintain a safe level of sap in the pan. Once sweet, anything you add to the pan you should then be able to draw off. For example...add 40 new gallons of sap...draw off 1 gallon of syrup..without going below a safe level of sweet in your pan. Then at the end of the season, you would very slowly and very carefully bring that last 3 gallons of syrup in your pan down to as low a level as you feel comfortable, drain the pan, and finish it elsewhere.

I don't use dividers in my 2x4. I just reestablish the gradient each new boiling day.

[Swingpure]

Yes, boiling 80 gallons of sap in a flat pan or a divided pan at the end of the day will give you 2 gallons of syrup. But in a 2x4 pan that 2 gallons of syrup might be like 1/4" or so. You would never bring the level down that low unless you like living on the edge. The idea of consuming 150 gallons or so in a 2x4 pan to sweeten it is that you can maintain a safe level of sap in the pan. Once sweet, anything you add to the pan you should then be able to draw off. For example...add 40 new gallons of sap...draw off 1 gallon of syrup..without going below a safe level of sweet in your pan. Then at the end of the season, you would very slowly and very carefully bring that last 3 gallons of syrup in your pan down to as low a level as you feel comfortable, drain the pan, and finish it elsewhere.

I don't use dividers in my 2x4. I just reestablish the gradient each new boiling day.

Thanks I think I understand it now. My sap levels at the start will be more like 2” as Dr Perkins had recommended. It is getting the 2” depth of syrup which is why it takes 150 gallons. It now makes sense to me. Thank you.

My openings are not circular so if I ever decided to plug them, I guess I could use some sort of flat plate, clamped to the divider.
https://share.icloud.com/photos/051ELT32Iyy38dQ23aaXPHu9A

I likely will not have to do that, as I will be boiling almost everyday, trying to keep up with my sap quantities and by the time the sap cools down, to when I start up again, will not be that long of time. It should not take too long to reestablish a gradient.

I have lots to learn, but one scenario is if a several days cold front moved in and shut down the sap flow, and I was not going to boil for a few days, those could be the times I “plug” the openings.

Thanks again for the answer on why it takes 150 gallons, it is always better for me when I’m understand it.

Gary

[DrTimPerkins]

With a smallish pan it may not make sense to try to preserve the gradient. Simplest solution would be to just draw off some near-syrup near the end of the boil, then once you start-up the next day, after your fire is started and nearing a boil, dump that near-syrup back into the partition nearest the draw off. This will hasten the reformation of a gradient.

[needmoremaples]

With a smallish pan it may not make sense to try to preserve the gradient. Simplest solution would be to just draw off some near-syrup near the end of the boil, then once you start-up the next day, after your fire is started and nearing a boil, dump that near-syrup back into the partition nearest the draw off. This will hasten the reformation of a gradient.

Smokey lake says to do this in their YouTube videos. You should check those out Gary

[Swingpure]

With a smallish pan it may not make sense to try to preserve the gradient. Simplest solution would be to just draw off some near-syrup near the end of the boil, then once you start-up the next day, after your fire is started and nearing a boil, dump that near-syrup back into the partition nearest the draw off. This will hasten the reformation of a gradient.

Thank you!

[Swingpure]

Smokey lake says to do this in their YouTube videos. You should check those out Gary

Thanks I have searched through a number of their videos and have not found it yet, but that is just a reflection of my search skills. The ones I found they simply put the lid on at the end of the day.

I will keep looking for it.

I will draw some off as Dr. Perkins recommended.