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Brewers can make their own invert syrup (Belgian candi syrup) by heating regular granulated table sugar, water, and a little acid. https://www.homebrewersassociation.org/how-to-brew/invert-syrups-making-simple-sugars-complex-beers/

The process involves heating the syrup well above the boiling point of water, so there is no separate water present in the finished product, but hydrolysis occurs, so the hydrogen and oxygen molecules are taken up by the sugar molecules.

The chemical reaction is : hydrolysis of sugar chemical formula

If I start with one unit, say one pound, of table sugar, how many pounds of syrup will I get?

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Ideally, you would obtain 1.05 times the weight of your sugar, because for 342 g of sucrose you would need 18 g of water. This is based upon the molar masses of both components.

This would of course almost be a physical impossibility, because that would mean that the contents are probably not liquid any more, and you would not be able to dissolve 342g of sugar into 18g of water.

To minimise the amount of water, use 100 mL of water (3 oz.?) per 250g (about half a pound) of sugar. First dissolve all the sugar at a temperature of 80° C (176°F), only then start to increase the temperature to the boiling point. Around 104 or 108° C (220°F) you will notice that the temperature does not increase for a time. I think that this is because water is evaporating from the mixture. So, the amount of water diminishes.

Last time I made invert sugar, with the above amounts, I think I got less than, or around 300 g invert syrup.

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This depends completely on how much water is left.

The total weight will be the sum of all weights less water evaporation (boil off).

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  • I just clarified the question. There is zero water left, but some atoms from the water end up in the syrup. – Dale Apr 6 '18 at 14:01
  • @Dale the article you mentioned most defiantly has water volume evaporation and additions. Revealed by the drying of crystals and the recomendation of using a wet brush or spray bottle to counter. You really won't get an exact weight unless you know all those additions / subtractions, or simply weigh your final product. – Evil Zymurgist Apr 6 '18 at 14:05
  • Having the syrup well above the boiling point of water for a "long time", I was thinking there was no more water left. There was certainly no steam. But if the reaction outputs (glucose and fructose) are solid, then I guess there must be water. The water content is probably determined by the highest temperature reached. – Dale Apr 8 '18 at 2:18
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According to this link, sugar heated to the lowest temperature in the Homebrewer's Association article (236°F) will result in a syrup with a 15% water content. The water content drops to 10% if the temperature gets around 250°F and drops to 1% if the temperature gets to 300°F.

As a sanity check, this article says that invert syrup gives 36 ppg (points per pound per gallon), whereas rock sugar gives 45 ppg, suggesting that there is 20% water content in the syrup.

So one pound of granulated sugar, heated to 236°F should yield 1.18 to 1.25 pounds of invert syrup and should be in the range of 36 to 39 ppg.

ADDITIONAL INFORMATION: This answer is being appended, about a year later.

Summary

An experiment was performed with a 4 pound bag of table sugar. Water was not measured (no way to measure evaporation), but the weight of the crystal sugar and the resulting syrup were measured. The result was that the invert syrup provides 36 gravity points per pound per gallon. This is agreement with the link above.

Process

The "4 pound" bag of sugar contained 1803g net weight. After bringing water and sugar to 237 degrees F, I measured the weight of the finished product, plus the residue on the equipment and it came to 2331g. The total in the jars was 2314g and the volume was 1638ml, so the density of the syrup was 1.412g/ml.

Result

This experiment indicates that one pound of granulated sugar will yield 1.29 pounds of invert syrup if the syrup is heated to 237F. The resulting density will be about 1.41g/ml.

Because table sugar is 46 ppg, this would mean that the syrup made by this process would be 36 ppg.

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