Before manufacturing silicone parts, it is important to select a finished durometer for the part or product that you will be molding. Depending on the requirements of the project, the silicone finished part may be near gel-like or very stiff. Durometer is a measure of hardness that is used in elastomers, polymers and rubbers. Hardness may have many definitions, but in our case with regards to Shore durometer, hardness is defined as a material’s resistance to indentation.
The Shore durometer scale was created by Albert F. Shore in the 1920’s. Originally, the result was just signified by a number, for example 50 durometer. As time progressed, multiple durometer scales were created. The Shore durometer scales that are most commonly used in plastics, rubber and silicone are the A, D and 00 shore scales.
There are two main differences amongst these scales. First, the configuration of the indenter that is pressed into the material is different with each scale. Second, the hardness range is different with each of the three scales. The Shore 00 Scale measures rubbers and gels that are ultra soft. The Shore A Scale measures rubbers that range from soft and flexible to hard with almost no flexibility. The Shore D Scale measures the hardness of hard rubbers and hard plastics.
Below is a table of common finished products and their respective durometers.
Here at Albright, we use the Shore A scale to quantify our molded silicone durometers. The Shore A scale ranges from 0 to 100. An example of a “0” durometer Shore A silicone molded part would be a very soft shoe insole. Near the opposite end of the scale, an example of an “80” durometer Shore A silicone molded part would be an o-ring seal or a stiff silicone kitchen spatula. Every day, Albright molds products in materials that range in finshed durometer from 10 to 80 on the Shore A Scale.
What materials and durometers have you molded parts in? What durometer Shore scale do your materials come in? How do you determine what durometer of material to use?
Please remember that the durometer selected will be based on the requirements of your project. If you need assistance determining a durometer for your next silicone project, Albright engineers and technical staff are here to help. In addition, we can provide samples of silicone in various Shore A durometers. Want samples of silicone durometers? Visit our free durometer sample page on the Albright web site.