Couple Questions

[OCHTO]

In looking at my sap vs. syrup totals I came to some questions so I ask those who know.
My sap hydrometer is calibrated at 38*F. A lot of my readings were taken mornings with ice in the tank, I think maybe 33 to 36 degrees. Will my hydrometer read high of low with lower sap temps?
Next, I boil with a 2 X 4 flat pan. It seems the higher my sugar content later in the afternoon, like when I have about 80 to 100 gallons in the pan, my evaporation rate goes down. Our theory is that it takes more energy to evaporate the concentrated sap.
Lastly, what would be a good bleach percentage in water to wash out my 5 gallon sap collection jugs? I'm thinking 1 pint. That would be a 40 to 1 ratio. Is that enough bleach to be effective? Otherwise I get mold in my jugs if I just rinse with water.
Thanks for your time.

[Haynes Forest Products]

One tea spoon per gallon is what I do. But if asked by an inspector say you use a test strip. Now A cup per gallon if your surface is bloody and man I do bleed a
lot in the sport of sugaring.

Now evaporation rate without considering draw off rate doesn't compute in my brain. Now with concentrate you do boil off less but get a better return on your draw off rate. :confused:

Colder denser warmer thinner

[ecolbeck]

The density of water is at its greatest at around 38 F but any correction for 33 F would be negligible. In other words your reading may be high because water is less dense at 33 F than at 38 but the error is not enough to matter.

It takes the same amount of energy to evaporate water regardless of the temperature that the water is boiling at. Your sense that your evaporation rate is slowing as the sap concentrates must be due to some other factor or is based entirely on your perception. I know I have certainly encountered the feeling that "this is really taking a long time so things must be slowing down."

[Russell Lampron]

The hydrometer reading will be higher at the colder temperature. I'm not sure how much difference 5* will make because I don't have a chart. When testing syrup it isn't much.

Why do you think that the evap rate is slowing down with the higher concentration percentage? Is the level in your feed tank going down slower or seeing less steam?

[OCHTO]

I was very pleased with my sap sugar content this year and it's reassuring to know it wasn't reading high due to colder sap.

Both my partner and I agree the boil rate goes down as the syrup thickens. We base this on how often we fill the feed pan. While it takes a certain amount of energy to boil water, a constant. Does it take the same amount of energy to boil a mixture of say 10% sugar and 90% water? Not a big deal, just interesting. I also thought that I was anxious to get the days boil over and that made time appear to go slow but I'm so busy during boiling that it feels like time flies. But it probably is a perception thing just surprised we both came up with same perception.

[ecolbeck]

I was very pleased with my sap sugar content this year and it's reassuring to know it wasn't reading high due to colder sap.

Both my partner and I agree the boil rate goes down as the syrup thickens. We base this on how often we fill the feed pan. While it takes a certain amount of energy to boil water, a constant. Does it take the same amount of energy to boil a mixture of say 10% sugar and 90% water? Not a big deal, just interesting. I also thought that I was anxious to get the days boil over and that made time appear to go slow but I'm so busy during boiling that it feels like time flies. But it probably is a perception thing just surprised we both came up with same perception.

Science is cool stuff. The presence of sugar does raise the boiling temperature but has no effect on the energy required to evaporate the water from the mixture. Similarly, sugar (or salt) will depress the freezing point of water but it doesn't take more energy to melt ice in the presence of sugar compared to pure water.

I'm curious to know what else might be going on that gives you the impression that the evaporation rate is slowing. Are you saying that your first boil of the season is always the fastest? In other words, once you have sweetened the pan and you come back for your next boil does the slower evaporation rate continue?

[Haynes Forest Products]

I'm still curious why no one is bringing up how much syrup they are drawing off when it comes to evaporation rate.e its like discussing MPH without divulging how many miles I went down the road but only discuss how much gas I keep putting in the tank.:confused:

I'm going out on a limb here and say the higher the concentration of sugar in the sap I feed into my evaporator the lower my evaporation rate .............BUT there is less evaporation because more of the liquid is going out the draw off and not up the cupola.

[MapleMark753]

One different but related aspect to look at is that you may be getting a carbon and ash build up on the bottom of your pan as the boil goes longer. And this may cause a slowing of the boil during any, but particularly longer boils. Are you able to clean/brush the bottom of your pan between boils? And dryer wood wood helps too because of incomplete combustion that may happen if wood moisture content is higher. And the grate can get a bit clogged with ash too, preventing an optimum amount of air getting to the fire. A good rake with a fire poker can clear that right out. Just a couple thoughts.
take care, Mark

[ecolbeck]

I'm still curious why no one is bringing up how much syrup they are drawing off when it comes to evaporation rate.e its like discussing MPH without divulging how many miles I went down the road but only discuss how much gas I keep putting in the tank.:confused:

I'm going out on a limb here and say the higher the concentration of sugar in the sap I feed into my evaporator the lower my evaporation rate .............BUT there is less evaporation because more of the liquid is going out the draw off and not up the cupola.

OK, how about this?

You have a certain distance to cover in your car, point A (sap) to point B (syrup). Water is evaporating as you drive. The faster you drive (MPH) the higher the evaporation rate. If you start with sweeter sap (through natural variation or RO) you are cutting down the distance you have to drive (you are starting closer to point B), but this is completely independent of how fast you drive.

The sweeter the sap you put into your evaporator the less vapor will need to go out the cupola and the greater a quantity of syrup will come out the draw off but the evaporation rate is the same regardless.

[ecolbeck]

One different but related aspect to look at is that you may be getting a carbon and ash build up on the bottom of your pan as the boil goes longer. And this may cause a slowing of the boil during any, but particularly longer boils. Are you able to clean/brush the bottom of your pan between boils? And dryer wood wood helps too because of incomplete combustion that may happen if wood moisture content is higher. And the grate can get a bit clogged with ash too, preventing an optimum amount of air getting to the fire. A good rake with a fire poker can clear that right out. Just a couple thoughts.
take care, Mark

These are good questions. This also brings up the point of why dry firewood is so important. When firewood is burned every ounce of moisture in it is converted to steam. This conversion of liquid water to vapor robs tremendous amounts of energy that could be going to heat the evaporator (or house). I've heard it said that firewood can be "too dry" causing it burn "too quickly". This is total bunk.