I received my material, but one of my containers was only half full. Is this a mistake? Was I shorted material?

Article courtesy of Smooth-On, Inc.

New users of Smooth-On rubbers, plastics, foams, pigments, powders and other materials understandably expect that, when they order a product, the containers they receive will be full. Sometimes that is the case, and sometimes not. It depends on the material you are buying and, more specifically, the density of a particular material.

Smooth-On rubbers, plastics and foams are dispensed into pints, gallons, 5 gallons and other containers by weight. It is the only way to ensure accuracy and consistency. Depending on the density of the material that you buy, the volume of the material in theses containers may be less or more. For example, a gallon unit of VytaFlex™ 20 urethane mold rubber contains 16 lbs. of liquid in both parts (A + B) and is 7/8 full by volume. A gallon unit of Brush-On 40 contains 18 lbs. of material – liquid in the Part A side and a heavy paste in the Part B side. Due to the density of the paste material, the Part B will only fill a gallon bucket ½ full volumetrically.

A good example for comparison would be the snack food industry. You buy a bag of potato chips and it's â…“ full, or a box of cereal that you open is ½ full. Potato chips, cereal and similar products are all packed by weight. It is the density of each individual chip or piece of cereal that will collectively determine how full the package is volumetrically.

Other Factors that Determine How Much Material is Packed into a Container

  • The mix ratio of a rubber, plastic or foam system. How many parts of A are combined with Part B of that system?
  • The commercial availability, economy and uniformity of different container sizes that allow us to get your material to you in good condition and ready to be used.

Pro Tip: Don't guess at the amount of material needed for your application by volume. Correlating the cubic inch per pound yield of the material with the cubic inches of your original (and possibly your mold box) is a more accurate determination for your material requirement.

Click here to go to Smooth-On's Material Calculators ›


This FAQ article is offered as a guideline and offers possible solutions to problems encountered during mold making and casting. No warranty is implied and it is up to the end user to determine suitability for any specific application. Always refer to the provided Technical Bulletins (TB) & Safety Data Sheets (SDS) before using any material. A small scale test is suggested to determine suitability of any recommendation before trying on a larger scale for any application.