Frequently Asked Questions on Boiling Maple Sap for Syrup

The principle of boiling down your sap is really easy. You basically want to boil off the water, so that you are left with the highly concentrated sugar-water (syrup). Typical ratios of sap to syrup run anywhere from 20:1 to 40:1, depending on the sugar content of your sap. Sugar maple trees have the highest sugar content, so often the ratio of sap to syrup for a sugar maple is on the order of 32:1 or so, at least in my experience. If you don’t mind ‘watery’ syrup, then you can get away with less boiling, so you end up with a higher yield, like 20:1.

How long does it take to boil Maple Syrup?

It takes about 5 hours of boiling to reduce 5 gallons of maple sap into 20 oz of maple syrup.

How much Maple Syrup can you get from 5 gallons of Sap?

A typical ratio for sugar maple sap to syrup is 32:1. So if you start out with 5 gallons of sap, you will end up with 20oz of Maple syrup.

How much does it cost to make Maple syrup?

Buying all the supplies to make Maple syrup for home use will have a one-time cost of about $200. After that the cost of propane will cost about $20/gallon of Maple syrup. The average price per gallon of Maple syrup in the U.S. is around $35/gallon.

How do I know when Maple syrup is done boiling?

Maple sap has finished boiling into Maple syrup once the temperature has reached 7ºF above the boiling point of water. In most places this is around 219ºF. For higher accuracy, use a refractometer and stop boiling the sap at 66% sugar content.

Can you stop in the middle of boiling maple sap, then start up again?

Yes, since sap is boiled for long periods of time, it is quite common to boil maple sap for several hours, add more sap while it is boiling, and then stop boiling before it is finished. Then, the boiling process is startup up again later on – for example the next day. This will not harm the sap or affect the quality. Some producers even boil continually, starting and stopping throughout the season, and only perform the finishing boil once at the end of the season! One thing to note is that the final product may end up slightly darker, due to the heating and cooling process.

My maple sap froze, should I remove the ice on the top?

Yes. Freezing maple sap is a great way to eliminate water and increase the sugar content of your sap through a process termed freeze distillation.

How does this work? When the temperature of maple sap decreases, water and sugar molecules are both moving around. Once the freezing point of pure water is reached, water ice crystals begin to form, but only once the correct structure of water molecules are in place next to each other, effectively forcing out the sugar molecules. The remaining water/sugar solution continues to increase in sugar concentration as more water freezes. The frozen part is a more pure concentration of water. A similar process is used in salt water desalination by natural freezing, particularly if repeated several times.


In practice, some of the sugar molecules get trapped between pure ice water crystals, resulting in irregular ice crystals with some sugar molecules adhering to, or trapped between, them. The result is typically not pure water ice, but rather ice with a sugar content somewhere between about 0 – 0.8% (depending on how quickly the sap froze – the slower the better).


The sugar content of pure sugar maple sap is about 3%. By removing the ice with a lower concentration of sugar, the remaining solution has an increased sugar concentration. By repeating the process multiple times, some claim it is possible to increase the sugar concentration to above 10%. Native Americans used this technique quite effectively.

Can maple sap go bad?

Yes. Maple sap becomes cloudy when it begins to go bad. Keep the sap close to 32 deg F, and boil it within 1 week of collecting it.

Should you keep a lid on the pot when boiling Maple sap?

No! The point of boiling sap is to eliminate water, by having a lid on the pot, the water condenses on the lid and drips back into the sap, repeating the process and increasing the amount of time it takes to boil sap into syrup.

Can you drink Maple sap directly from the tree?

Yes! I highly recommend it, tapping your maple trees And drinking the sap makes a very refreshing drink! However, be prepared for the fact that it isn’t very sweet. The sugar content is relatively low compared to something like apple juice. This is why maple sap is generally boiled down into syrup; in order to increase the sugar content.

A Few Words On Boiling with Propane

Refill vs Exchange

The 20 lb propane tanks I use hold about 4.6 gallons of propane. I recommend that you take them somewhere to be re-filled, as opposed to exchanging the cylinders – and here’s why. When you exchange the cylinder, the tank you are exchanging for is not filled all the way full and typically only holds about 3.5 gallons of propane. I usually refill the tanks at Tractor Supply, where currently the price is $2.19/gallon. So to fill one of these tanks is about $10.

How Long Does One 20 lb Tank of Propane Last?

The tank will usually burn for about 15-20 hours total (depending on how high you turn up the heat). This is enough to boil down about 4 batches of sap (5-gallons each).

Detailed Picture Guides on How to Make Maple Syrup at Home

For detailed instructions on how to tap maple trees, boil maple sap, and perform the maple syrup finishing boil, check out these articles:

Making Maple Syrup – Part 1 – How to Tap Maple Trees for Sap
Making Maple Syrup – Part 2 – How to Boil Maple Sap
Making Maple Syrup – Part 3 – How to Perfect the Finishing Boil