Soap Colorant Dosage Calculator

How soap colorants work:

Soap colorants are added to the soap batter (usually at trace in cold process) to achieve the desired color. The amount needed depends on the type of colorant, the color intensity desired, and the total oil weight of the batch, not the total batch weight including lye water.

Dosage is always based on oil weight: Colorant % = (Colorant weight / Total oil weight) × 100

This is the industry standard because oil weight is the consistent base. Water and lye amounts vary with recipes, but the oils are what carry the color.

Standard dosage rates by colorant type:

Weight equivalents:

• 1 tsp mica ≈ 2.5 g
• 1 tsp oxide ≈ 3 g (denser)
• 1 tsp titanium dioxide ≈ 3.5 g
• 1 tsp ultramarine ≈ 3 g
• 1 tsp charcoal ≈ 1.5 g (very light)
• 1 tsp clay ≈ 4 g
• 1 tsp botanical powder ≈ 3 g

These are close enough for soap and nowhere near close enough for anything that has to be repeatable. A teaspoon of mica scooped straight from the jar and one levelled with a knife differ by a third. If you plan to make the same colour twice, weigh it.

Worked example: A 900 g oil batch, medium purple using mica:

• Rate: 1 tsp per lb of oils
• Oil weight in lbs: 900 / 453.6 = 1.98 lb
• Micas needed: 1.98 × 1 = ~2 tsp = ~5 g
• For a swirl: divide into portions (e.g., 2/3 white titanium dioxide, 1/3 purple mica)

Color stability in soap: Not all colorants survive the high pH (9–10) of cold process soap:

• Stable: Micas, oxides, ultramarines, titanium dioxide, charcoal
• May morph: Lab-created FD&C dyes (some shift dramatically)
• Will fade: Most botanical powders (turmeric browns over time, spinach goes olive)
• Reliable botanicals: Indigo powder (blue), alkanet root (purple), annatto (orange), cocoa powder (brown), paprika (orange-peach)

Dispersion tip: Always pre-disperse powder colorants in a small amount of lightweight oil (1 tsp colorant in 1 tbsp oil) before adding to soap batter. This prevents clumping and streaking. For titanium dioxide, use a mini frother or stick blender to ensure smooth dispersion.

Take the dispersion oil out of the recipe, do not add it on top. This is the step that catches people. Two tablespoons of oil is about 27 g, and on a 900 g batch that is an extra 3% of oil the lye was never calculated against. Superfat goes from the 5% you chose to 8%, which is soft, greasy soap that goes rancid early. Hold back the dispersion oil from the recipe oils before you weigh the lye. Water-dispersible colorants can go into part of your lye water instead, which sidesteps the whole problem.

Multi-color and swirl techniques: Divide your soap batter at trace and color each portion separately. Use the same total colorant dosage, just split across portions. For example, a two-color batch at medium shade uses 1 tsp/lb in each colored portion.