Clarify beet juice by adding a small amount of slaked lime or wood-ash lye, letting the impurities settle and pouring off the clear liquid, then boil it down; to crystallize, keep evaporating with stirring in a shallow pan until the syrup is concentrated beyond what it can hold when cool, then drain the molasses from the crystals. Sucrose dissolves to about 67% by mass at 20 C and about 83% at 100 C, which is why syrup stored at 66% sits close to crystallizing.
Clarification removes suspended and dissolved impurities from sugar juice, and crystallization forms solid sucrose crystals from a concentrated syrup, leaving molasses behind.
Two Separate Jobs
Clarifying cleans the juice before it is boiled. The sugar guide’s step is to add a small amount of wood-ash lye or slaked lime, which precipitates impurities, let the juice settle and pour off the clear liquid. It gives no quantity for the lime or lye (“a small amount”), and this page cannot source one, so do not guess: test on a small batch, use the least that gives a clear liquid, and note that too much leaves a taste and a dark colour. Large sugar factories follow liming with a second step to remove the excess lime; the guide describes nothing like it for a village.
Crystallizing is optional. The guide says to continue evaporation with stirring in a shallow pan until sugar crystals form, and to drain the molasses, the liquid that will not crystallize, which is also useful as a sweetener. The alternative is beet syrup, simpler and needing no crystallization skill (Sugar Beet Processing).
The Solubility Limit
Sucrose dissolves in water up to a limit that rises with temperature. Recalled handbook values: about 204 g in 100 g of water at 20 C, which is 204 ÷ 304 = 67% by mass, and about 487 g in 100 g of water at 100 C, which is 487 ÷ 587 = 83% by mass.
- A syrup at 66% sugar, a common storage concentration, is just below saturation at 20 C. A little extra evaporation, or a cooler cellar, pushes it over the limit and crystals form in the jar.
- To make crystals on purpose, boil to more than about 67% and cool, so that the syrup is supersaturated when it cools. The hotter and more concentrated, up toward 83%, the more sugar can come out as crystals on cooling.
- Raw juice also carries other solids, and the molasses holds the sugar that stays dissolved with them. The guide gives no figure for how much of the sugar ends as crystals instead of molasses, and I cannot source one, so measure your own crystal weight against the syrup you started with.
What You Need
- Slaked lime or sieved ash lye, in small measured trials (Lye from Ash)
- A settling vessel with a tap or siphon, so the clear liquid can be drawn off
- A wide shallow pan for the final boiling
- A thermometer, since the boiling point of the syrup rises as it concentrates
- Cloth or a drip bag to drain the crystals from the molasses
Method: Clarify, Concentrate, Crystallize
Step 1: Strain the extracted juice. Step 2: Add a tiny quantity of lime or lye with stirring. Watch for flocculation. Stop adding once the liquid clears on standing. Step 3: Let it settle, then draw or pour off the clear liquid without disturbing the sediment. Step 4: Boil in a wide pan, skimming foam, to syrup. Step 5: For crystals, continue to concentrate, stirring, then let the syrup cool undisturbed; stir to promote crystals. Step 6: Drain the molasses through cloth, and dry the crystals.
Keep the juice from becoming acidic while it is hot, because acid and heat split sucrose into simpler sugars and spoil crystallization (recalled chemistry).
Common Mistakes
- Overdosing with lime. It darkens and flavours the sugar.
- Pouring off the sediment too. The settled mud has to be left behind.
- Overheating syrup. It scorches and darkens.
- Throwing away molasses. It is a sweetener in its own right.
Safety
Lime, lye and a pan of concentrated sugar
Slaked lime and ash lye are caustic: wear gloves and eye protection and keep them away from children. Concentrated sugar syrup burns more severely than boiling water because it sticks; do not stir a boiling pan with the face over it, and keep a bucket of cold water within reach to cool burns (Thermal Injury Care). The solubility figures are recalled and not from this corpus.
What’s Next
- Learn next: Yield per Acre — what an acre of beets yields as sugar
- Combine with: Shelf Life of Sweeteners — storing syrup and sugar