Slip Casting

Slip Specific Gravity Calculator

Calculate slip specific gravity from weight measurements to determine slip consistency for casting.

Reviewed by ClayCalc Editorial · Updated

g

Fill a 1-litre container with well-mixed slip and weigh it (subtract container tare weight).

g

Total dry materials weight in your recipe.

g

Water added to dry materials (1 g ≈ 1 mL).

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Results

calculate

Enter your measurements above and click Calculate.

What is Specific Gravity?

Specific gravity (SG) is the ratio of a liquid's density to the density of pure water (1.0 g/mL). A slip with SG 1.78 weighs 1.78× as much as water — it is 78% denser than water due to the suspended clay solids.

SG = weight_of_1_litre_of_slip (g) ÷ 1000

SG Reference Guide

SG RangeApplication
1.20 – 1.35Very thin engobe / terra sig
1.40 – 1.75Engobe / slip decoration
1.75 – 1.85Casting slip (ideal)
> 1.90Too thick — add water

Method & review note

About this calculation

Uses weight, volume and ratio relationships. Product data sheets and measured viscosity/thixotropy take priority over generic presets.

Reference: USG — No. 1 Pottery Plaster. See the editorial methodology for testing, precision and corrections.

Input handling: Values are sent to the ClayCalc server for this request and are not written to the application database.

Read the Pottery Plaster Mixing

Frequently Asked Questions

What is the ideal SG for casting slip? expand_more
Casting slip typically works best at SG 1.75–1.85. Below 1.70 the slip is too thin and cast walls are weak and slow to firm up in the mold. Above 1.90 the slip may not pour or flow properly.
How do I measure slip SG? expand_more
Weigh exactly 1 litre (1000mL) of well-mixed slip. Divide that weight by 1000 to get the specific gravity. For example, 1780g = SG 1.78. Use a dedicated 1-litre slip jar for consistent measurements.
My slip SG is correct but it does not cast well — why? expand_more
SG alone does not tell you about viscosity or thixotropy. The slip may be over-deflocculated (gel-like) or contain old, settled material. SG should always be combined with a flow test (30-second viscosity test with a flow cup).