The traditional electrolyte concentration of 165 grams H2SO4 to 1 liter (1 liter = 1000 grams) of water is 165/1000 = 16.5% by weight. This corresponds to a 9.4% concentration by volume. Since no one commonly weighs sulfuric acid, water, or other liquids, its usually measured by volume in practice.
To sum it up:
Concentrated sulfuric acid; 100% by weight and volume.
Commercial battery acid; 35% by weight, and 19.2% by volume.
"Professional" electrolyte; 16.5% by weight, and 9.4% by volume.
Caswell's 1:2 electrolyte; 6.4% by volume.
LCD electrolyte; 4.8% by volume.
Bath temperature is important but I wouldn't call it critical, it effects pore size mostly. If the anodizing is done "open loop" by voltage, temperature becomes much more important, as does the dissolved aluminum content of the electrolyte. This is because both effect the electrical conductance of the electrolyte. Closed Loop anodizing (constant current) automatically compensates for differences in electrolyte conductance.
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