I. Core Basis for Viscosity Selection

1. Balance between defoaming efficiency and dispersibility

   Low-viscosity dimethyl silicone oil (e.g., 50~200 cSt) has short molecular chains and strong fluidity. It can quickly penetrate into the ink system, reduce surface tension, and destroy the stability of bubble films, thereby achieving efficient defoaming. At the same time, its good spreadability helps it disperse evenly in the ink, avoiding quality issues (such as ink stratification or oil spots after drying) caused by excessive local concentration.
2. Compatibility with ink components

   Tattoo ink usually contains water, alcohol, glycerin, resin, pigments (e.g., iron oxide), and other components. Low-viscosity dimethyl silicone oil is a non-polar substance, which has good compatibility with non-polar resins (e.g., acrylic resin) and pigments. It can effectively improve the dispersibility of pigments and reduce agglomeration. For example, in alcohol-based inks, 50~200 cSt silicone oil can dissolve quickly and form a stable defoaming system without affecting the fluidity of the ink or the film-forming property after drying.
3. Avoiding drawbacks of high viscosity

   Although high-viscosity silicone oil (e.g., above 1000 cSt) has a long foam-suppressing time, it has poor fluidity and tends to form local agglomeration in the ink, leading to uneven defoaming. In addition, high-viscosity silicone oil may increase the consistency of the ink, affecting the smoothness during tattooing, and even causing the ink surface to become sticky after drying.

II. Industry Practices and Typical Cases

1. Application of standard viscosity models
   According to the industry standard HG/T 2366-1992, the viscosity specifications of dimethyl silicone oil cover 10~10000 mm²/s (i.e., 10~10000 cSt). Among them, models such as 201-50 (50 cSt), 201-100 (100 cSt), and 201-200 (200 cSt) are widely used as defoamers in the coating and ink industries. These models also perform well in tattoo ink:

• 50 cSt: Suitable for scenarios requiring rapid defoaming and high ink fluidity (e.g., water-based inks).
• 100~200 cSt: While maintaining defoaming efficiency, it better balances the stability and dispersibility of the ink, especially suitable for inks containing resin or high solid content.

2. Technical reference from international brands
   For example,some dimethicone of international brands , 100 cSt and 200 cSt silicone oils are recommended for coating systems that require efficient defoaming and low volatility. Although this series is not directly targeted at tattoo ink, its technical characteristics are highly consistent with the needs of tattoo ink. In addition, medical-grade simethicone (e.g., 350 cSt) is commonly used for defoaming, but its higher viscosity may be more suitable for special ink formulations that require long-term foam suppression.

III. Usage Precautions

1. Dosage control

   The dosage of dimethyl silicone oil is usually 0.1%~0.5% of the total mass of the ink. Excessive use may lead to excessively low surface tension of the ink, resulting in sagging or abnormal gloss after drying; insufficient dosage will result in an insignificant defoaming effect. It is recommended to determine the optimal addition amount through small-scale testing.
2. Mixing process

   Silicone oil should be added in the later stage of ink preparation (e.g., after pigment dispersion), and low-speed stirring (to avoid introducing new bubbles) should be used to disperse it evenly. For high-viscosity inks, the silicone oil can be pre-mixed with part of the solvent first, then gradually added to the system.
3. Compatibility testing

   Silicone oils from different brands may vary in purity and additives (e.g., antioxidants). Before large-scale production, it is recommended to conduct compatibility testing on the selected silicone oil, including observing the stability of the ink, drying time, adhesion, and skin irritation.

IV. Summary

It is recommended to choose dimethyl silicone oil with a viscosity of 50~200 cSt, among which the 100~200 cSt range has the best overall performance. Silicone oil in this range can not only defoam quickly but also have good compatibility with ink components, while avoiding processing and performance issues caused by high viscosity. For specific models, you can refer to the 201-50, 201-100, and 201-200 series in industry standards, or similar products from international brands. During use, the dosage must be strictly controlled and the mixing process optimized to ensure the stability and safety of the ink.By the way,Since silicone oil is used in tattoo pigments, please select a suitable brand based on your own safety assessment.

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