Thoughts on Insulating Pot

[Frank Ivy]

Ok, so here's my thought.
I have no evaporator.
Yes yes, a horrible affair, I do understand, but the fact nonetheless.

I just got my stainless steel stock pot - about 25 gallons.

So the reason this is not nearly as good as a proper evaporator pan is because 1. the tall sides will act as radiators and 2. there is less surface area on the bottom through which to direct heat to the liquid.

But my understanding of physics tells me that the surface area of the liquid inhibits evaporation at first because heat is lost - that is why a covered pot boils faster than an open pot.

(Given this, the ideal design for an evaporator would be a container that has insulation on all sides except the flame side and that has a suitable vent to release the gaseous water vapor. In other words, an insulated, whistling tea pot would boil off a quart of water faster than an open pot.)

So #2 I can't change - it is what it is.

#1 I can possibly reduce by wrapping the stock pot in ceramic insulation.

My plan is to have the stock pot sitting on a grate over a fire with a sheet metal horizontal surround skirt located at about 2" as a block-off plate above the grate so that the fire can hit the bottom and lower 2" of the pot but can't go higher. From there until an inch or two below the top I'll have the mineral wool blanket. The top of the pot will be open.

If you assume that there is very little heat transmission through the insulation, the depth of fill of liquid in the pot should be irrelevant to boiling.

Any thoughts on this?

[KenWP]

A tea pot would probbably not boil off water as fast as a open pot due to the fact you have a restriction and the top of the pot would condense some of the steam and return it to the bottom. If the opposite was the case all pans would be covered already. As to insulating the pot that might work as the metal above the sap level probbably does radiate heat and therefore cool it somewhat. The other thing you could do it use a steel plate over the fire with a hole big enough for the pot to sit in a couple inches. The closer to the fire the hotter it will boil and you would stop air currents from getting to the bottom ofthe pot.

[Frank Ivy]

A tea pot would probbably not boil off water as fast as a open pot due to the fact you have a restriction and the top of the pot would condense some of the steam and return it to the bottom.

Opa!!! Could well be. Depends on many factors.

But, all else being equal, an insulated volume with an escape vent will boil off liquid faster than an open pot.


If the opposite was the case all pans would be covered already.
Not so! I respectfully disagree.
There are many other reasons why an evaporator pan is open - easy to clean, cheaper, can inspect syrup, and so on. An open system is probably much better for a lot of reasons, but rate of turning water into steam is not one of them.

In terms of boiling the water only, with nothing else in mind, the best way to do it would be to have an insulated container with a small vent port. If the container was insulated, then there would be no "condensing" to worry about because the walls and roof of the container would reach the boiling point of the liquid and stay there.

In a tall pot scenario what you have is a lot of surface area that is exposed to the air, so figure 100 degree air is cooling the pot on the sides. Not good.

If I add rock wool, then heat will not be able to leave the sap through the metal, and so the heat is either retained in the sap, or heats the water to the vapor point and drives it off as steam.

I'm just playing with physics here! It'll be fun to experiment.



As to insulating the pot that might work as the metal above the sap level probably does radiate heat and therefore cool it somewhat. The other thing you could do it use a steel plate over the fire with a hole big enough for the pot to sit in a couple inches. The closer to the fire the hotter it will boil and you would stop air currents from getting to the bottom ofthe pot.

Yes! That IS the plan. I think it should work.

Thanks for the thoughts.

[DanE.]

Frank, I think you want a double wall pot. just like the stove pipes we use. they keep the heat in, or if you look at it the other way, keep the cold out. have it open on the bottom , maybe shaped like a funnel to bring the excess heat up through it and opened at the top. Or you can cut the pot down to the size you need......:o

Dane.

[RileySugarbush]

Ideally you would have all surfaces that are wet on the inside be subjected to very high temperatures on the outside. In your insulated wall pot,the best you could approach is the boiling temp if the insulation is perfect.

Try jacketing the pot with a air gap of one inch or less all around the pot and open top and bottom so that the combustion gasses flow closely along the side of the pot. Do your best to force most or all of the combustion gasses through this gap. Now you have at least doubled or tripled the heat transfer area. if you still want to insulate something, insulate the outside of that jacket to keep losses to the atmosphere low.

We have done this on turkey friers and it makes a big difference.


Edit: I just read what DanE wrote. Just like that!

[Frank Ivy]

Thanks DanE.


Do I risk burning/scorching the sap if I get the fire right up against the pot? It's SS and about 7mm thick on the bottom.

[RileySugarbush]

The only way you can scorch it is if it goes dry. Maybe a little around the surface like a ring if you get the sides really hot. It won't hurt your syrup at all.

[vtjeeper]

Thanks DanE.


Do I risk burning/scorching the sap if I get the fire right up against the pot? It's SS and about 7mm thick on the bottom.

This is my first post on here but I have been around reading a lot for a while. I started sugaring last year and the reason for me posting now is that I have experience in the turkey fryer sugaring arena. I boiled all levels from 2/3 full to dry and warped and scorched the bottom of a ss pot. so, as long as you don't let it go dry the bottom will be fine, but, this experiment you have of heating the sides I do not really support. the pot will be fine, and it will not ruin the syrup. But it will burn the syrup at the line where the liquid surface is, and as it boils down and this line gets lower it will keep burning lower and lower and you end up with a large band of burnt sugar around the wall of the pot. also flecks of it all in your syrup. burned sugar means you lost sugar and therefor finished syrup. ideally you would have lots of heat up the sides no higher than the liquid. I like the 2 inch idea as long as you don't let the liquid get below the 2 inches. some insulation or winblock is good. but if you made a plate on top of a firebox for the pot to sit right down into like a steam table in a buffet you would have the insides of the pot blackened and burn a lot of sugar and I'm guessing would not be good for the sides of the pot.

sorry if this is kindof long winded. but good luck to you, this year I'm going to boil in a 2x6 pan and finish in a turkey fryer.:)

[Frank Ivy]

sorry if this is kindof long winded. but good luck to you, this year I'm going to boil in a 2x6 pan and finish in a turkey fryer.:)

Thanks for the post! Good info, and I'll act accordingly.

[jordy95]

hay vtjeeper with your experience with the turkey fryer how hard do you boil and try not to use to much gas. you know the differants you want a hard boil but not be an high.thanks jordy95

[vtjeeper]

hay vtjeeper with your experience with the turkey fryer how hard do you boil and try not to use to much gas. you know the differants you want a hard boil but not be an high.thanks jordy95

I used 3 different burners last year. 2 of them had more of a center firing jet setup. the 3rd burner was probably about 5 inches in diameter and was a cast loop with holes around the top of it. half the holes were clogged so it wasn't burning very good but I was desperate to get all the sap boiled so I used it. the flames were lapping up the sides of that pot the whole time, which is why I burned sugar all around the inside. the other 2 burners I kept the flame pretty high, I wanted to a raging boil, didn't have much of any burning with them. I don't think I had them turned up all the way, there was a point at which I didn't think it would evaporate any faster than it was so I dind't just keep them up as far as they'd go. oh, in the last couple hours I decided to look at that burner closer cause one of my propane tanks ran out. I stuck a nail through the clogged holes and switched propane back onto that burner and it worked much better. I could have done that in the beginning and not burned up all that yummy sugar. :rolleyes: