Mold Star 30 mixing calculator
Calculate Mold Star 30 Part A and Part B from a batch target or either measured component.
1:1 Part A:Part B by volume
How to use this calculator
- Choose measuring vessels or scales; the calculator selects the matching product ratio.
- Select your starting point and enter the amount.
- Measure both components on the selected basis and follow the product’s preparation and mixing instructions.
Worked example
For 500 mL combined silicone, the 1:1 volume recipe needs 250 mL Part A + 250 mL Part B. On scales, a 500 g combined batch instead needs 500 × 100 ÷ 196 = 255.102… g A and 500 × 96 ÷ 196 = 244.898… g B. Equal volume does not mean equal weight.
Questions about this calculation
Is Mold Star 30 mixed 1:1 by weight?
Its published weight recipe is 100 parts A to 96 parts B. The 1:1 recipe is by volume. For example, with 100 g Part A already measured, add 96 g Part B; with 100 mL A, add 100 mL B.
Can I start from Part B already measured?
Yes. Choose Part B already measured. The calculator keeps that quantity fixed and derives A. For 96 g B it returns 100 g A, giving 196 g combined.
How does this convert mould volume to mixed mass?
The product page publishes a mixed density of 1.12 g/mL. An estimated 500 mL mixed quantity is approximately 560 g. This is a mixed-material estimate; it does not substitute equal weights for the component volume recipe.
Does this apply to other Smooth-On silicones?
This page is pinned to Mold Star 30. Check the precise product label and current technical bulletin before using a recipe for another grade or silicone.
Sources and measurement basis
Use the exact current instructions for your product, version and market. Review date: 16 October 2026.