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p-shrinkage-cast

P-03 shrinkage by cast cylinder

2026-09-29 · By The Candle Bench · Repeats 3×

Shrinkage is measured as a physical contraction, not inferred from a formula. A 60 mm cylinder is cast in a steel mould, released, and measured at three temperatures, because a wax that shrinks 9 % cold may shrink 14 % on the way down and drag a glass wall with it.

MethodCast steel cylinder, dimensional measurement at three cooling stagesRepeats3×equip5Quantities produced3Environment controlCasting room at 21 C and 45 %RH, mould held at 32 C between pour and release

Procedure

  1. 01

    Warm the steel mould to 40 C, apply a single thin film of release agent and wipe off the excess with a lint-free cloth.

  2. 02

    Pour at the temperature named on the specimen page, in one motion, and fill to 3 mm above the top line to allow for contraction.

  3. 03

    Hold the mould at 32 C for one hour, then release the cylinder with a brass drift and measure its diameter at three heights with a digital calliper.

  4. 04

    Measure again after 4 C conditioning for two hours and again after 24 h at 21 C. Shrinkage is the diameter at 21 C as a percentage of the mould bore.

  5. 05

    Cut the cylinder in half with a heated wire and measure the wick-well void depth, which is reported separately from the shrinkage figure.

Two waxes can share a cold shrinkage figure and behave completely differently in a vessel, because the number that matters during cooling is the shrinkage at the temperature where the wax is still plastic. So each cast is measured three times: at the moment of release, at 4 C, and after 24 h at room temperature.

Mould bore模具内径
Cylinder height圆柱高度
Casts per specimen每牌号浇注次数

Instruments used

  • Split steel mould, 60 mm bore, 90 mm tallmachined to +/-0.02 mm
  • Digital calliper, 0.01 mm resolutionMitutoyo 500-196
  • Brass release drift, 12 mmno brand
  • Heated wire cutter, 0.4 mm nichromeno brand
  • Circulating bath for the 4 C stageGrant LT ecocool

Sampling table

Casts per specimen 3
Measurement heights per cast 3
Cooling stages measured 3 (release, 4 C, 21 C)

Quantities produced

  • Shrinkage at 21 C, %diameter over mould bore
  • Intermediate shrinkage at 4 C, %reported separately
  • Wick-well void depth, mmfrom the cut section

Environment: Casting room at 21 C and 45 %RH, mould held at 32 C between pour and release

Protocols cited