Purify crude salt until a sample dissolves leaving almost no residue, tastes plainly salty rather than bitter and does not turn damp in an open room, then grade the batch by use and grain size and store food salt apart from the rough salt kept for hides and livestock. Grading is a safety step as well as a quality step, because the grade decides which salt may go into food, cheese or a cure.
Part of Salt Production & Sourcing
Purification and grading is the cleaning of crude salt and its sorting into uses by purity and grain size, so each batch goes only where it is safe and suitable.
Purify To A Test, Not To A Feeling
The steps of purification are in Removing impurities and bitter minerals. Grading starts from the tests that tell you whether it worked:
- Residue test. Dissolve a weighed sample in warm water, filter, dry and weigh what remains. The less, the better.
- Taste test. A bitter or metallic taste fails food use.
- Damp test. A spoonful left on a dry dish in an open room overnight must not turn damp.
- Look. White or lightly grey, free of visible grit, clay or brown streaks.
No home test finds heavy metals or other poisons, so grading cannot rescue salt from a contaminated source. Source comes first.
A Practical Grading Scheme
These are suggested working grades for a community, not a published standard:
| Grade | Use | What it needs |
|---|---|---|
| Food, fine | Table and cooking | Purified; passes all four tests; fine grain |
| Food, coarse | Curing, brining, pickling, cheese | Purified; passes all tests; coarse grain |
| Rough | Hides, livestock, ice and snow, cleaning | Unpurified or partly purified; known source; not for food |
Coarse, purified salt for curing is the grade that the meat-curing batch depends on (Dry cure ratios and rub formulas), and the one most worth keeping in good supply. Grain size is the subject of Grain size control.
Keep The Grades Apart
Labelled containers are the whole defence. Rough salt that finds its way into a brine tub can add bitterness, dirt and unknown contaminants, and any curing premix, if you have one, must never be stored with or look like food salt (Cold-smoked sausages and bacon explains why). Use different containers, different markings and different shelves.
What You Need
- A scale and a sample dish
- Warm water, filter cloth and a drying place for the residue test
- Labels and containers for each grade
- A batch record: date, source, method, test results, grade
Method: Grade A Batch
Step 1: Take a sample from the middle of the batch, not the top.
Step 2: Run the residue, taste and damp tests.
Step 3: Sieve for grain size.
Step 4: Assign the grade, label and record it.
Step 5: Re-purify any batch that fails food grade, or downgrade it to rough.
Common Mistakes
- Grading by appearance alone.
- Mixing batches after grading.
- Letting a downgraded batch slip into food use.
- Not recording the source. A clean-looking salt from a bad source is still bad.
Safety
Grading cannot detect poisons
Any curing premix containing nitrite is a poison if mistaken for salt and must never be graded, stored or issued with food salt. The tests above catch dirt, bitterness and dampness; they cannot catch lead, arsenic, industrial chemicals or radioactive minerals. Do not grade salt from a source you do not know as food salt, and never eat salt made from brine or seawater that came from near mines, oil, industry or sewage.
What’s Next
- Learn next: Grain size control — shaping crystals to suit each use
- Combine with: Storage & Distribution — keeping the grades in good order