boiling pan question

[stifflej]

I am new to this, going to tap my first trees as soon as PA weather allows (which may be July around here) and have been reading about different pans which can be used. My question is about pans with divides, from what I have read, it states that you always pour the sap in one corner, and from the opposite corner you can drain just about finished syrup. I am not sure I can follow this logic (just can't picture how it would work). Can someone explain, possibly with some pics so I can get a grasp on it? Also, if I were to use 2 full size steam table pans, 6" deep, could I put a connection between them to create this setup, and a valve at one end that I could use to drain off the finished sap? Also, could I just use threaded steel pipe to make the connections?

Sorry for what is probably a stupid set of questions, but I don't have any one that has ever done this before.

Thanks for the help.

[SilverLeaf]

not a dumb question! I don't have pics, but basically the process works because the dividers create what is, in effect, a big long trough. the liquid in the trough doesn't really move laterally on its own, so what's at one end of the trough never gets mixed back together with what's at the other end of the trough. the only time the liquid ever moves laterally is when more is added to one end. That pushes the liquid down the trough a little ways because liquid always wants to level out. So because you are consistently adding the sap in the same end of the trough, the liquid is just gradually, over time, working its way to the other end. And over time what happens is that only liquid that's been in the pan for awhile makes it to the far end, by the draw off valve, so that becomes syrup, while what's at the beginning of the trough where you're adding it, stays diluted a bit.

[SilverLeaf]

the only time the liquid ever moves laterally is when more is added to one end.

I should say, it also moves laterally when you draw off at the far end too, because liquid has suddenly been removed from one end.

[PerryW]

You will have a hard time getting any flow with a small setup.

1) Just set the two pans over the fire and fill both pans half full with sap and boil as fast as possible until they are both 1/4 full.

2) Use a small pan with a handle as a dipper and ladle as much sap as you dare from the back pan into the front pan. (If you get too shallow, you will scorch the back pan)

3) Now refill the back pan with more fresh sap (until half full) and boil like crazy untill the back pan is 1/4 full and repeat step 2.

Eventually, your front pan will develop syrup using this method. If you run out of sap and haven't developed syrup in the front pan, drain the front pan and finish it off on the stove. Just be careful, because it will boil over and make a mess REAL QUICK when you approach syrup.

[Groves]

I'm a batch guy as well, but one thing I haven't figured out is what benefit is there to the transfer of the sap from one pan to another?

It shouldn't make it any lighter because the sap is still boiling on the stove the same amount of time.

Why not just boil them as low as you dare and refill both and keep going?

[vtsnowedin]

I'm a batch guy as well, but one thing I haven't figured out is what benefit is there to the transfer of the sap from one pan to another?

It shouldn't make it any lighter because the sap is still boiling on the stove the same amount of time.

Why not just boil them as low as you dare and refill both and keep going?
Mostly it is a long boring process and moving it from one pan to another gives you something to do that helps you mark your progress. I've had three ss lobster/stock pots on the stove plus the bottom of the wifes pressure canner all cooking away on the stove. On a small set up like a backyard barrel or a stove two quarts is a good batch size. So you are starting with about twentyfive gallons of sap and have to reduce it down to one gallon before you can get it into one high sided stock pot to finish it to syrup. You need a pot with ten or twelve inch sides as it will foam up with big syrup bubbles when you get close. Going from 2.5% sap in the canner to 6% sap in lobsta pot #1 to 24% in #2 and 48% in#3 works pretty good. You can stop anytime and finish off whats in pot #3 so you get somthing done each day rather then have pans or pots full of 12% sap for days on end.Also boiling nice fresh sap all the way to syrup in one session will give you better grade then stopping and starting and storing it half finished will.
Good luck with your first year Stifflej.

[Groves]

It took me a year to get it through my head that your evaporation rate is only going to go up as the surface area of the bottom of your pan goes up.

It won't go up with hotter fire as long as you're boiling.

This is why kettles and stock pots are so slow. I have a whole year of turkey fryer maple syruping before it all clicked. Slow and expensive.

This is why guys run their pans as shallow as they can. Why waste energy keeping all of that other non-boiling liquid hot?

Go for wide and shallow (compared to stock pots) pans and you'll notice the difference. Even one steam table pan is so much more surface than most stockpots.

[stifflej]

I have been looking for pans specifically for evaporating, but holy crap are they expensive...I don't want to put to much money into it if it is only going to be a one year thing...I guess I will try to find some steam table pans and use them, they seem to be cheaper, even if I buy new ones off of ebay...

[wcproctor]

Go to a restaurant supply shop and buy used stainless steel pans (12 x 20) they work mint and buil a block arch in the back yard

[Fishgill]

I don't want to put to much money into it if it is only going to be a one year thing..

If your like most everyone here this won't be just a one year thing :lol: . We started with a large stock pot last year and this year our pan is 2'x4'. :)

[emo]

If you are using steam table pans, if you transfer from one pan to the next the 2nd and after pans don't have to reheat the sap that is transfered to them. I use 3 and only add to the first pan which never quite boils due to the position over the fire. I use it like a pre-heater/1st pan. The other 2 pans boil fairly easily. I use a soup ladle to transfer and keeping the level just deeper than the ladle seems to work well. I have checked the temp on the 1st pan when I add cold sap to the pan and have watched the temp drop from around 190-195 back to about 150.

[mapleack]

StiffleJ,
Where are you at in PA? I'm in Indiana County, it's always nice to see more people making syrup in PA.
-Andy

[PerryW]

I'm a batch guy as well, but one thing I haven't figured out is what benefit is there to the transfer of the sap from one pan to another?

Because it allows to to actually finish syrup off on your evaporator. The level would get too shallow if you kept adding sap to both pans. Neither pan would ever get to syrup, unless you had a lot of sap.

Your evaporation rate is the same either way, but by concentrating syrup in the front pan, you can pull that batch off sooner and it spends less time on the heat as the method of adding sap to both pans. It works even better with three pans.

[Groves]

The level would get too shallow if you kept adding sap to both pans.

I don't really understand this sentence. I think if you keep adding sap to both pans the level only goes up. It's true that if you can add it slowly enough to not kill the boil it helps. If you want to use one of your pans essentially as a preheater then that's ok. It does speed you up over a single pan, but it's not faster than just boiling away on both pans equally.



Your evaporation rate is the same either way, but by concentrating syrup in the front pan, you can pull that batch off sooner and it spends less time on the heat as the method of adding sap to both pans.

It's true that boiling syrup for longer times can make darker syrup (it's up for debate whether this is good or bad), but using that logic you should never add more sap, just take what's in the pan down to syrup and pour it out to finish elsewhere.

Obviously this is really hard to do without scorching due to the very small final amount in the pan. So, we do end up adding more of something, and every time it's something that needs more boiling. If it didn't need more boiling we would just take it inside to finish and find something else to add that did need boiling.

So for most of us batch guys, I still maintain that all of our ladling between pans does little but scorch the pan edges where we drip. Setting up a gradient with multiple pans doesn't get it off the fire any sooner unless we really do have more than one batch.

And if we do have more than one batch, then by all means take off the first one before you start the second.

Probably our greatest help would be a preheater in the stack combined with a way to very slowly add our preheated sap. If we kill the boil in that one pan we've sacrificed as a preheater, then it's not really helping us boil, and we've just moved our preheater from the stack to the fire.

The best part about all of this....it still tastes great at the end. The season is upon us!

[KenWP]

I'm a batch guy as well, but one thing I haven't figured out is what benefit is there to the transfer of the sap from one pan to another?

It shouldn't make it any lighter because the sap is still boiling on the stove the same amount of time.

Why not just boil them as low as you dare and refill both and keep going?

I would have to say if you use a three pan system and tranfer the sap foreward al lthe time to the front pan you would gain on cleaning up pans. Then only the front pan would get the nitre build up and need cleaned all the time instead of cleaning 3 pans of niter. Also like said when you get almost done the level of 3 pans would be extremly low unless you had a lot of sap to start with. On a 18inch by 16 inch pan a gallon of syrup is just a bit less then 2 inchs deep so with 3 pans the same size you would be like 2/3 of a inch deep which is sort of scarey.

[KenWP]

I'm a batch guy as well, but one thing I haven't figured out is what benefit is there to the transfer of the sap from one pan to another?

It shouldn't make it any lighter because the sap is still boiling on the stove the same amount of time.

Why not just boil them as low as you dare and refill both and keep going?

I would have to say if you use a three pan system and tranfer the sap foreward al lthe time to the front pan you would gain on cleaning up pans. Then only the front pan would get the nitre build up and need cleaned all the time instead of cleaning 3 pans of niter. Also like said when you get almost done the level of 3 pans would be extremly low unless you had a lot of sap to start with. On a 18inch by 16 inch pan a gallon of syrup is just a bit more then a inch deep so with 3 pans you would be about 7/16 of a inch deep which is tres scarey to say the least. You could burn that in seconds if you don't keep a eye on it.

[wnybassman]

I'm a batch guy as well, but one thing I haven't figured out is what benefit is there to the transfer of the sap from one pan to another?

It shouldn't make it any lighter because the sap is still boiling on the stove the same amount of time.

Why not just boil them as low as you dare and refill both and keep going?

I used a three pan system for the last 10 years. My smallest pan was a warming pan. Small volume so the sap warmed quickly. I added that sap to the middle pan, which was my largest pan. You always want to maintain boil, so that pan had high volume so the incoming sap had little impact on overall temperature. It killed the boil, but only briefly. From that pan I ladled into the medium sized pan which took it to the sweetest point. That boil never got killed. I took it down in that pan as much as I dared, then took it into the house to finish.

With this system I could usually get 40+- gallons down to 2 gallons in about 10-12 hours.

Basically I moved sap from one pan to the next so I didn't kill the boil.

[Haynes Forest Products]

[QUOTE

It won't go up with hotter fire as long as you're boiling.

Groves Im confused about this statement so your saying there is no differance in boiling? I have seen a 3X10 under full boil as hot as he could get it burning dry oak slabs and we tossed in a feed bag full of old sap lines and in about 1 min the pan front to back boiled over lost 75% of everything we cooked.

Every year I do a FISH BOIL in Wisconsin and we boil the fish Potatos and onions over a 30 min period and as its boiling we do what is called the BOIL OFF. What we do is toss about a pint of Kerosene on the fire and it super heats the BOILING water and it boils over cleaning all the scum out of the pot. So there is a differance in boiling

[KenWP]

If it never got too hot nobody would ever boil a pot over on the stove either. Not that I ever did it.

[Groves]

Groves Im confused about this statement so your saying there is no differance in boiling?

My statement referred to the amount that is evaporating per hour when it's under a FULL boil with a medium hot fire verses the amount that is evaporating per hour when it's under a FULL boil with a HOT HOT fire.

There is no difference. Full boil is full boil.

Now, we all know that there's a difference in evaporation between a simmer and a full boil, but a simmer is simply a boil thats only happening on a small portion of the bottom of the pan.

It's most applicable to people going at it on a turkey boiler like I was. You can add all the heat you want. A hundred welding rosebuds if ya like, but if it's already at a full boil, then all you're doing is wasting heat.

Increasing your evaporation rate means increasing the surface of metal being heated. This usually means a pan with greater area on the bottom, and of course includes all the flue pans, which are simply adding even more surface area from which boiling can occur.

[vtsnowedin]

I don't know if the amont of time people spend worring about "not killing the boil" is worth it. To evaporate sap you have to add a certain amount of BTUs to it. If dumping in a ladel of sap kills the boil it means you haven't got enough fire but the fire you have will get the job done as soon as it delivers enough BTUs. Letting the whole pan cool down while you do something on the 'Honey Do" list and then reheating it is a waste of fuel but if your anywhere close to a boil a BTU is a BTU and steam happens. Perhaps some Mechanical engineer can weigh in and give us the skinny on this.

[Groves]

I don't know if the amont of time people spend worring about "not killing the boil" is worth it.


I left all my mechanical engineering when I switched to metallurgy, but even that was some time ago. I'll take a stab at it.

Boiling doesn't simply occur when a liquid reaches it's boiling temperature. No sir.

For boiling to occur, it must reach it's boiling temperature AND add a certain amount of energy as well. This extra energy is called the heat of vaporization.

A liquid that boils at 212 will be at 212 right before boiling and during simmering and during boiling. The temperature will not rise if its "boiling faster".

Here's something that's true: If it's not boiling, then it's not evaporating in large quantities. Of course it's evaporating like any other hot cuppa coffee or whatnot, but it's not evaporating quickly in that manner we like to call....boiling.

Killing the boil is therefore indeed killing the evaporation rate, that's for sure.

So, if you can add your sap (preheated or not) in such a way that you already have the BTUs being added to BOTH account for the new sap's lower temp AND keep imparting that heat of vaporization, then the boil (the quick evaporation we're after) continues.

This usually means adding it in a however small a trickle is necessary to maintain the boil.

Of course if you can just flip a switch and increase the BTU you might not need to worry about it, but for a fixed BTU situation (I'm giving 'er all she's got, captain) then your evaporation rate is maximized by never killing the boil.

I'm no scientist, though.

[stifflej]

Cambria county, not to far from you, in between Altoona and Johnstown, not far off 22.

[3rdgen.maple]

Groves I am not understanding your input. Can you tell me why my evaporation rate goes up when I have a hotter fire going? If my pans are boiling from front to back are you saying I am wasting wood by getting that sucker to boil harder? What about the guys who get a full boil in there pans get an increase in evaporation rate when they add a blower to the arch to get the btu's up? Here is what I am thinking. It has something to do with surface area right? If you get the pans boiling harder and the sap is covering a larger surface area as it jumps all over the place I have to believe it is evaporating off more by taking advantage off the suface area it comes in contact with. I could be wrong and have been before and I am no engineer either, just a redneck boiling syrup.

[RileySugarbush]

3rdgen,

Groves has it right. You just have to consider what is meant by more BTUs...

BTUs are a measure of heat. The more heat that transfers to the sap, the higher its temperature gets until it hits it's boiling temperature. Then the heat goes into changing liquid into gas and that jump in energy is the heat of vaporization just as Groves mentioned. Its important to know that the heat of vaporization is big. For a given bit of water ( or sap) it takes about 5 times ( I forget the exact ratio) as much energy to vaporize it than it does to heat it from 32°F to 212°F. Thats is why we can't get tremendous gains in rate with preheating, only about 10 or 15%.

Now to your question. The amount of heat transferring from fire to sap is determined largely by the difference in temperature between the sap and the fire. More difference = more heat transfer. Of course more surface area in important too, but given a specific pan all you can do is get the bottom of the pan hotter to make it boil harder. We do that with more fuel and more oxygen and good mixing of the two.

You had a great observation about the boiling helping itself to boil.
Another help getting heat into the sap is that mixing which increases the convective heat transfer from the wet side of the pan to the sap. Not really the change in wet area but kind of a similar thought. Strangely this effect falls off the harder it boils and heat transfer efficiency drops some. (Too complicated to discuss here)

Look up heat transfer in wikipedia. There is a section on "Boiling Heat Transfer" and also a section on "Condensation heat transfer" which is what happens on our preheater tubes.

In our evaporator pans the heat transfer is:

1) Convection from hot gas to the metal of the pan. Hotter gas and bigger pan area both increase this.

2) Conduction through the pan. Thin metal is best. Copper is better at this than plain steel and plain steel is a bit better than stainless. Stainless is used because it is, well, stain less. Strong too, so it can be thin.

3) Convection again, this time from the hot pan to the liquid. And again, area helps.

So here is the short version:

More area exposed is more evaporation, high temps in your arch leads to more evaporation. High temps at your stack base indicate high temps under you pan and that is good for evaporation rate, but not for efficiency. That high temp in you stack is lost energy. This has been discussed on this site several times.

We are managing very complicated processes for a bunch of rednecks!!!

[PerryW]

groves said:
My statement referred to the amount that is evaporating per hour when it's under a FULL boil with a medium hot fire verses the amount that is evaporating per hour when it's under a FULL boil with a HOT HOT fire.There is no difference. Full boil is full boil.

While the temperature is the same whether you are boiling with a medium fire or hot hot fire ; the evaporation rate certainly goes up with a hot hot fire. Sure, if you are cooking hot dogs, it doesn't matter because the temperature is the same, but evaporation would follow conservation of energy i.e. MORE FIRE = MORE EVAPORATION.

Try this experiment on your kitchen stove to proove my point:

Get two identical pans of water boiling on your stove. Set one burner to boil at a medium boil and set the other burner on high and see which pan empties quicker.

[3rdgen.maple]

More area exposed is more evaporation, high temps in your arch leads to more evaporation. High temps at your stack base indicate high temps under you pan and that is good for evaporation rate, but not for efficiency. That high temp in you stack is lost energy. This has been discussed on this site several times.

Okay is that not what I said. Right wrong or indifferent my burner is on high. I completely understand what BTU are. Riley you said " given a specific pan all you can do is get the bottom of the pan hotter to make it boil harder" that is not what Groves said unless I am not understanding him correctly, the way I read it was it does not matter how hot you get the pans it is not going to boil any harder.
And just like Haynes was saying but on the kitchen stove. If higher temps do not mean more boil then why can I get a pan to boil over on high and turn it down to a controlled boil where it does not overflow? I understand water reaches a boiling point and gets no higher but I am not boiling water I am boiling sap and if the temps never reached 7 degrees above where water boils then how will we ever make syrup?

[Haynes Forest Products]

Groves/3rdgen Im starting to see the light. NOW when we do the boil off in the fish kettle we are really just super heating the very small layer of water that is contacting the pan causing the gases to explode/super expand (lack of the right word) and boil over. Sadly it probably doesnt add much heat to the bulk of the water:cry: in that short time.

NOW for some fun Because I live at 6400' above sea level liquids boil at a lower temp. So now Im thinking its boiling but it aint making steam as fast as it does at sea level RIGHT????? Because the TEMP of the liquid is lower I need to BOIL it longer for the same outcome.

[3rdgen.maple]

Haynes you are speaking my language now. Layman terms. I think it is about time we tap some darn trees cause I am going nuts....

[KenWP]

No it boils away at the same rate becasue of lower air pressure and what ever. In Peru you can drink the coffee hot out of the pot almost they live so high and it takes all day to cook anything in a pot.

[RileySugarbush]

I hadn't noticed the claim that "full boil is full boil" and nothing can increase it. That isn't the case. If you can get more heat to transfer into a liquid, then the evaporation rate will increase. There is no scientific definition of a full boil.

Getting the max heat to transfer to the liquid in our situation is simple:

First expose a maximum surface area to the heat source. That is what the flues are for of course.

Next, get the heat source on the bottom of the pan as hot as you can. That is why we are splitting the wood fine and adding combustion air. More exposed fuel surface with plenty of oxygen.

There are lot's of subtleties and trade offs, but that is the basics.

Most of us have seen examples of brief and incredible boil rates, like when we toss some kindling or cardboard into an already hot fire. Suddenly a very hot fire and maybe a boil over! That is really just taking the second point above to an extreme with the cardboard acting like really fine split wood with lots of surface area!

[Big_Eddy]

Folks are confusing the temperature of the liquid and evaporation rate. Water / Sap / Syrup that is boiling is at the same temperature, regardless of simmer, boil, rolling boil, spitting boil. That's where the "heat of vapourization" that Groves mentioned in Post 22 comes in. Add BTUs to cold water and the temperature rises gradually until it reaches the boiling point, then it remains at that temperature while you continue to add more BTU's. Every molecule of water requires a specific number of BTU's to change state from water to steam - that's the "heat of vapourization".

For our evaporators - more BTU's transferring from the fire to the boiling sap means equates to more "heat of vapourization" added to the boiling sap. In other words more BTU's transferring means more molecules of water are changing from sap to steam.

If you increase the fire temperature then more heat transfers to the sap and you convert boiling sap to steam faster. Plain and simple. The sap temperature stays the same - but you boil off faster.
If you increase the surface area - you transfer more heat to the boiling sap - you convert sap to steam faster too. Same effect.

Now here's the real challenge - How do you maximize evaporation rate while minimizing fuel inputs? I.e. how do we transfer the highest possible percentage of fuel energy into steam, without sending it up the stack? That's the real challenge.

[PerryW]

I hadn't noticed the claim that "full boil is full boil" and nothing can increase it. That isn't the case. If you can get more heat to transfer into a liquid, then the evaporation rate will increase.

thank you RileySugarbush!

It was driving me crazy that people were saying a medium boil would make steam at the same rate as a hot-hot fire!

After boiling sap for 30 years, I've learned that a slow boil with wet wood means a long night in the sugarhouse.

Click below to see a hot-hot fire (and with no stinkin noisy blower):

http://vid6.photobucket.com/albums/y235/perryW/HPSyrupBoil2Small.flv

[KenWP]

Just remember that what me and haynes were talking about is the fact that water boils at a lower temp the higher you go. If you were on top of MT Everest water boils down around 180. It evaporates at the same speed because of lower pressure on it.
If you could boil sap at a simmer and get that same evaporation rate as a hard boil we could make 50 gallons of syrup per cord no problem. But with out a hard rolling boil it takes all day to get it to evaporate.

[3rdgen.maple]

Well it pretty much sounds like we are all on the same page at this point. Glad that was all worked out. For awile there I was trying to figure out if I was going nuts or not:D Hope I did not offend anyone.

[PerryW]

Ken,

I'm thinking of hauling my sap up to the top of Mt. Washington to boil there at 6288'.

At one time they talked about an evaporator that had a closed pan above it that ran at a vacuum so that the boiling temperature of the upper pan was lowered. The steam from your pans was used to boil sap in the upper pan.

[RileySugarbush]

For awile there I was trying to figure out if I was going nuts or not:D Hope I did not offend anyone.

By now it should be clear we are all nuts.

[Cabinet man]

Great posts guys! I am doing an experiment this year and will possibly go beyond what many of you are saying, and should enhance the evaporation rate per btu put in. I totally agree with more surface area and hotter fire, no question. I am adding something to the mix with the heat and surface area and its not air. I am concerned about killing the boil with this, however if it does not, oh baby..

If it works as the testing went this summer, the 50 gallons per cord might be possible. We are hoping for a full scale test this weekend.

Many things are stacked against us, but we will see come March. I am crossing my fingers.:D

[RileySugarbush]

Phaser on overload?

[JuniperHillSugar]

Cold fusion?

[Haynes Forest Products]

This is what can happen when you lock yourself in a room and alternate watching TOOL TIME and BACK TO THE FUTURE for 48 hrs stright

[vtsnowedin]

But Cap'n I'm giviner all shes got. Any moor an the millenium crystals will shatter.

[Cabinet man]

Its a cross between Haynes and an atom smasher, I mean sap smasher.:lol: I did run out of millenium crystals. Do you have a source?

I knew I would catch heck for that one!!

Really what I did was found something that was used many years ago for syrup, tested, supposedly proved to be better. The study said 30 times more efficient than using a traditional pan system. There was no problems with flavor or color. I simplified the concept that I found and installed it.

Now my question is if it was as good as they said it was, why are we only seeing pan systems? We will be running this with a pan instead of their sytem. so it is definitely different. We will see shortly. The nice thing is that I can pull it off in about 2 minutes and run her the way we were last year. Didn't cost an arm and a leg either. Will be fun to see how it works.

I will elaborate more as we go as I don't know what to expect as of yet.

[Cabinet man]

Well here are the results. There is no doubt it works. We increased our average gph by about 50%. Our sap was very low in sugar content so led to long boils, but we turn it on set the controls and can let her run. It does pull a lot of heat (killed the boil) though. I think that our setup needs a hood to keep the cold out of the pan. We could hold it at 205-210, but need more surface area to heat. I think that with wood pushing it hard it would incease quite a bit.

The 50% is a combination of burner heat shields, pan side shields, preheater that maintains 200+ degrees.

We made very light and tasty syrup, best we ever made this year. The setup did not set the world on fire, but I think that it is a proof of concept and I will be expanding on it next year with a raised flue, and adding a 2x4 divided pan.

Any way we look at it we could not have run this much sap last year with a stock flat pan on Lp. We made 40 + gallons most batches were excellent color and flavor.

Hope you all had a great season.