In praise of shallow pans

[40to1]

While still waiting (procrastinating) on getting a blower system or an RO, I am spending this season running the sap levels in the pan really low. I know there are too many variables to account for from season to season, but low sap levels in the pans really seems to make a difference.

Previous years I had about an inch of sap in the pans, but the is year I'm running at about a 1/4 inch to a 1/2 and the difference seems remarkable.
The boil seems harder which allows me to add sap faster (which, as counter-intuitive as it may sound, does not raise the sap depth.)
It seems that I can pull off more syrup sooner and for extended stretches.

I don't know if there's any data out there about the efficiency gradient of shallow levels, but I like what I'm seeing!

[TerryEspo]

That's interesting.
Maybe there is something to running shallower pan depth.

1/2" sounds scary though. I wonder If running 1" is better than 2" if your able to stand guard and babysit the pan.

I hope someone can jump in and share what they know about lower pan depth.

[Letcher Family Farms]

We have a Leader Half Pint, and we continuously run it very shallow, around a 1/2 inch. Only way to get an aggressive boil, but you have to stay on top of things.

[maplestudent]

I'm no expert (by a long shot) but I'm wondering if you guys have AUF and what kind of wood (and dryness of it) are you burning?

[mellondome]

1in is better than 2in 3/4 is even better. With 1 in, you only have to heat half the sap at a time, and the bubbles only have to gonhalf as far to break.

[Pauly V]

how are you able to draw off running at 1/2 inch? that barely makes it out the hole and spigot.

[pyro]

I have been thinking about this a lot lately. Other than the initial warm up time of the larger volume, I've had trouble understanding why 1" is any faster or better than 4". But I, like most people, have seen similar results so am convinced its true.

The only theory I could come up with is steam is likely formed mostly at the pan surface. When steam is formed at the pan surface it rises up through the liquid which is at a cooler temperature. This surrounding liquid cools down the steam slightly. Therefore the less depth you have, the less the steam is cooled.

Just my theory. I might check with some thermal experts at work.

[adk1]

I have run ar shallower pan depths before and I end up usually getting into trouble. If I had two float boxes that regulated each pan I would run shallower in the flue pan for sure. One thing to make certain of is that all your pans are level

[Sugarmaker]

"Beware the shallow syrup depth!"

Regards,
Chris

[pyro]

Just wanted to update to say my theory in last post is not correct. Discussed with some thermal experts. The steam that is generated is also at 212F (unless superheated which in this case is not) so it can not cool down as it is passed through a deeper volume of sap (assuming the liquid boiling and adequately mixing).

So the only difference is the heat loss to the sides of the pan. Running shallow reduces this surface area. Simple as that.

I thought I see the same behavior with shallow depths, but I've convinced myself its just perception. Especially since the boil responds much quicker to adding new wood.

[Bucket Head]

When you decrease the depth of the sap, your increasing the ratio of heat produced to the amount of liquid that heat has to boil. The same increase in boil can be seen in a flue pan when the sap level is held to just covering the flues instead of an inch of sap over the flues.

And Chris' warning from above goes for both type pans. The shallower the depth, the quicker disaster can strike. Very shallow boils can be done but you need to be right there watching it.

[smokeyamber]

Has anyone noticed that even with the pan as level as you can get it, on a divided pan the liquid in the the channel nearest the draw off is lower than that by the draw ? Also I can't run as low as 3/4 since the draw hole will not allow that low a draw... I have seen the pans with a draw box that allow for a full drain of pan via the draw, I like that design, but that does not seem to be the current design used.

I will be running a bit lower this year now that my float box has proven the be reliable, but I plan to keep a spare bucket of sap for any emergency fills...