Premium Very Soft Addition Silicone for Professional Pad Printing and Industrial Printing Applications

Wacker ELASTOSIL® RT 620 A/B is a pourable, room temperature-curing addition silicone (platinum-cure) for the production of printing pads. The product cures at room temperature with a Shore A hardness of 17, a translucent end product, and shrinkage of a maximum of 0.1%. With a pot life of 35 minutes and a tack-free cure time of 4 hours at 23°C, this system is suitable for efficient production processes. The mixing ratio is 10:1 (A:B) by weight, with the platinum catalyst located in component B. Use only components with the same lot number. ELASTOSIL® RT 620 A/B is ideally suited for applications where exceptional ink transfer, long mechanical life, and stable softness at high production volumes are essential.

Key Benefits

• Shore A hardness 17, exceptionally soft: the low hardness ensures optimal adaptation to irregular surfaces and maximum ink absorption and release in pad printing.
• Tear strength ≥ 12 N/mm, long service life: excellent resistance to tearing and puncturing guarantees a long and stable use of the pad, even at high production volumes.
• Elongation at break 900%, flexible and resilient: the extreme elongation prevents cracking under mechanical stress and makes the pad suitable for complex printing forms.
• Pot life 35 minutes, ample processing time: the high reactivity combined with a workable pot life allows for careful dosing and pouring, even when adding silicone oil thinner.
• Shrinkage ≤ 0.1%, dimensionally accurate: the almost shrinkage-free curing guarantees dimensionally accurate pads that can be used immediately after demolding without post-processing.
• Ingredients assessed for food contact: the manufacturer has assessed the ingredients against Regulation (EC) 1935/2004 and BfR Recommendation XV Silicones, among others. With appropriate processing the material is suitable for the manufacture of food contact materials, with compliance of the finished article to be ensured by its producer. The full status per region is set out further down this page.

Typical Applications

• Production of printing pads for pad printing on ceramic, porcelain, and glass surfaces
• Printing of plastic parts with irregular or curved surfaces, such as electronics and automotive components
• Pad printing on promotional and advertising articles with complex 3D geometries
• Industrial marking and coding on metal parts and tools
• Production of printing aids for applications involving food contact, where the manufacturer of the finished article ensures compliance

Processing Instructions:

1. Stir component A and component B separately and thoroughly before use, so that any settled filler is completely incorporated.
2. Weigh component A and component B in a 10:1 (A:B) weight ratio. Note: use only components with the same lot number.
3. Mix the components slowly and thoroughly for at least 3 minutes with a spatula in a figure-8 motion to minimize air entrapment.
4. Optional: degas the mixture in a vacuum chamber for 5 to 10 minutes for a bubble-free end product.
5. Pour the mixture into the mold or the pad printing form within the 35-minute pot life.
6. Allow to cure at room temperature (23°C) for at least 4 hours (tack-free) to 24 hours for full mechanical properties. Curing can be accelerated by applying heat.

The hardness of the pad can be gradually reduced by adding Wacker Silicone Oil AK 35. With 20 wt.% oil, the Shore A hardness drops to approximately 8; with 50 wt.% to Shore A 1 and Shore 00 35. This offers complete control over the pad properties for each printing application.

Manufactured by Wacker Chemie AG, global market leader in the development and production of silicones for industrial and technical applications.

Food Contact Regulations by Region

The overview below is taken from Wacker's Regulatory Product Information for ELASTOSIL® RT 620 A/B, version 1.19, last amended 17 July 2026. The assessment concerns the raw material and not the finished article.

• European Union, Regulation (EC) 1935/2004: with appropriate processing, suitable for the manufacture of materials and articles intended to come into contact with food in accordance with Article 3 of this Regulation, provided the material is of suitable purity and is not classified as hazardous under the European classification and labelling rules. Compliance of the finished article must be ensured by its producer.
• European Union, Regulation (EU) 10/2011: not applicable, silicones are excluded from this Regulation.
• European Union, Regulation (EC) 2023/2006: not applicable, this product is a raw material.
• Germany, BfR Recommendation XV Silicones: the ingredients comply. Restriction for the cured elastomer, volatile content maximum 0.5%.
• France, Arrêté of 25 November 1992: compliant. Total migration from the finished article maximum 10 mg/dm² or 60 mg/kg, volatile content maximum 0.5%.
• Spain, Real Decreto 847 of July 2011: compliant. Total migration maximum 10 mg/dm² or 60 mg/kg.
• Switzerland, Ordinance SR 817.023.21: the ingredients are listed in Annex 9.
• United States: a food contact statement can be provided separately upon request. The Regulatory Product Information states neither FDA compliance nor any 21 CFR section.
• China, GB 9685-2016: the additives are listed in table A.3 or A.7, the platinum catalyst is regarded as NIAS with a migration limit of 0.01 mg/kg food or simulant. GB 4806.16-2025: the siloxane starting substances are listed in table A.1. GB 4806.1-2016: the product complies.
• Brazil and Mercosur: the base polymers and fillers are listed in ANVISA IN 435/2026 and/or Mercosur GMC Resolution 34/2025. Restrictions, platinum residue maximum 50 mg/kg in the end product, volatile content maximum 0.5%, extractable content maximum 0.5%.

The admissibility of the ingredients does not mean that the end product is considered safe for food contact by regulatory authorities. Responsibility for the finished article rests with its manufacturer. ELASTOSIL® RT 620 A/B is a pad printing silicone with Shore A 17 and has not been assessed for biocompatibility, skin contact or medical suitability.

Important Warning: Inhibition in Addition Silicones

Please note: This is an addition silicone (platinum-cure). These silicones can be inhibited by sulfur, nitrogen, amino compounds, and metal salts. If you are unsure whether the materials you are using (gloves, spatulas, molds) contain these substances, please do a small test first. Inhibiting substances are found in, among others, latex gloves, some plasticines, condensation silicones, 1-component silicone sealants, and certain 3D printing materials. If in doubt, apply a layer of polyvinyl alcohol (PVA) as a release layer.

Professional Support

ELASTOSIL® RT 620 A/B is available in various packaging sizes and can be combined with Wacker Silicone Oil AK 35 for precise hardness adjustment. Please contact us for technical data sheets, processing manuals, or product advice.