Silicone oil (also sold as silicone fluid, PDMS, or dimethicone; CAS 63148-62-9) is a clear, colorless polydimethylsiloxane fluid bought by viscosity grade. RawSource supplies it in bulk, from 10 cSt to 100,000 cSt, in pails, drums, and IBC totes, with a lot-specific Certificate of Analysis (CoA) on every shipment, for industrial manufacturing, formulation, and OEM buyers.
This page does one job: match the viscosity grade to your duty, show the typical spec to expect, and get you to the right product page with a complete RFQ. The wider silicone range lives on the bulk silicone supplier hub; the chemistry is covered in what silicone oil is.
What is silicone oil?
Silicone oil is linear polydimethylsiloxane: a chain of alternating silicon and oxygen atoms, each silicon carrying two methyl groups, with trimethylsiloxy end caps. The registry entry for this trimethylsiloxy-terminated polymer is CAS 63148-62-9 (NIST WebBook; EPA CompTox DTXSID0049573). The RawSource per-viscosity product pages list the same polymer under the generic dimethicone registry number 9006-65-9; both numbers describe trimethylsiloxy-terminated PDMS.
“Silicone fluid,” “PDMS fluid,” and the INCI name “dimethicone” all describe this one polymer.
Because it is a polymer, there is no single molecular weight. Chain length sets viscosity, so the industry names the grade by its nominal kinematic viscosity in centistokes (cSt) at 25 °C, measured by capillary viscometer under ASTM D445. A “350 cSt” order is a grade, not a lot measurement. The CoA reports the measured value, typically within a tolerance band around the nominal figure.
What stays nearly constant across the ladder is the property set that justifies the premium over mineral oil: surface tension near 21 mN/m, a flat viscosity-temperature slope, thermal and oxidative stability, water repellency, electrical insulation, and chemical inertness. What changes is film thickness and pumpability. Decide the viscosity first; everything else on the RFQ follows from it.
How do you choose a silicone oil viscosity?
Match the centistoke grade to the duty, then confirm it with a sample on your own equipment. The table covers the grades most bulk buyers order; the full viscosity guide walks the entire 0.65 to 500,000 cSt range.
| Grade (cSt @ 25 °C) | Typical duty | Notes for the buyer |
|---|---|---|
| 10 cSt | Spreading, carrier fluid, light lubrication, mold release | Thin and mobile; open-cup flash point about 163 °C, lower than the heavier grades |
| 50 cSt | Release, light lubrication, general dielectric fluid | General-purpose low grade; not the moisture-controlled transformer specification |
| 100 cSt | Spreading, carrier, light lubrication, polishes | Balanced flow and film; common formulation grade |
| 350 cSt | General-purpose release, lubrication, polishes, plastic care | The most-ordered grade; durable low-migration film, slower spreading than 50 to 100 cSt |
| 1,000 cSt | Release agents, mechanical fluids, light damping | Higher cling; still pumpable with standard drum pumps |
| 10,000 cSt | Damping, anti-vibration, additive base | Heavy; plan heated or positive-displacement transfer |
| 60,000 cSt | Vibration control, high-temperature antifoam base (refinery cokers) | Heavy; specify handling equipment in advance |
| 100,000 cSt | High damping, specialty compounding | Near-gum; agree the transfer method before ordering |
The trade-off is direct. A low-viscosity fluid wets and spreads quickly, but the film is thin, it migrates, and the light grades are more volatile. A high-viscosity fluid gives a persistent film and strong damping, but it needs positive-displacement pumps, warmed lines, or pre-dilution to meter.
If your process falls between two grades, order the lighter one for coverage-limited jobs (release, polish) and the heavier one for film-limited jobs (damping, sealing). Blending two ladder grades to an intermediate viscosity is standard formulator practice; if you need one, say so on the RFQ.
Applications by industry
Viscosity and the purity or moisture spec behind it decide the job. The industrial uses guide covers each mechanism in depth; here is what each sector buys and why.
Lubrication and release
Rubber, plastic, and die-casting shops run 10 to 350 cSt fluid as a mold and process release, and 100 to 1,000 cSt as a lubricant for plastic-on-plastic, rubber, and light-load metal contacts where hydrocarbon oils would swell elastomers or gum up. Silicone oil is not an extreme-pressure lubricant on its own; for heavily loaded steel gears, keep a conventional oil. The 350 cSt grade is the sensible first sample for release duty because its film stays put between cycles.
Damping and hydraulic
Viscous dampers, torsional vibration dampers, and instrument fluids use 1,000 to 100,000 cSt fluid because silicone viscosity changes far less with temperature than a mineral oil of the same room-temperature viscosity. Specify the operating temperature range on the RFQ; the CoA viscosity is at 25 °C and the damper designer needs the curve, not the point.
Transformer and dielectric
Dielectric duty is where “50 cSt” causes the most expensive confusion. The general-purpose 50 cSt ladder grade is an adequate insulating and heat-transfer fluid for non-critical equipment. Transformers and fire-sensitive electrical installations need the silicone transformer oil specification instead: a moisture-controlled 50 cSt PDMS supplied on an IEC 60836 / ASTM D 4652 basis with acceptance testing per IEEE C57.111 and dielectric breakdown around 50 kV as a typical value. Order that product for transformer fills, not the general ladder grade.
Textiles
Textile finishing plants buy 350 to 1,000 cSt fluid as a thread and needle lubricant, a base for silicone softener compounding, and a slip component in fabric finishes. Straight PDMS gives slip and a dry hand; durable softness on cellulosic fabrics usually calls for a functionalized (amino) silicone instead of the straight fluid, so tell us the fiber and the effect you want.
Personal-care raw material
Formulators buy the same polymer under its INCI name, dimethicone, typically at 100 to 1,000 cSt, as a raw material for emollient, slip, and film-forming functions in skin, hair, and color formulations. RawSource sells it to manufacturers as a bulk ingredient; finished-product claims, safety substantiation, and labeling under cosmetic regulations belong to the formulator.
Coatings additives
Coatings makers use low-viscosity PDMS as a flow, leveling, and slip additive and heavier grades as a defoamer base, each at fractions of a percent. The caveat is the one every paint chemist knows: stray silicone is the classic cause of fisheyes and craters, so keep silicone oil handling physically isolated from any line that paints or coats parts. The silicone fluids for industrial manufacturing hub lists the grades stocked for these additive roles.
Bulk supply, grades, and quality control
Every ladder grade is straight, unmodified PDMS; the grades differ in viscosity and, for the transformer product, in moisture and dielectric testing. Typical values for the most-ordered grades:
| Grade (cSt) | Specific gravity @ 25 °C | Flash point, open cup | Pour point (approx.) | Volatility |
|---|---|---|---|---|
| 10 | 0.935 | ≈ 163 °C | ≈ −65 °C | Higher than the heavy grades; expect measurable loss at elevated temperature |
| 50 | 0.96 | > 260 °C | −50 to −70 °C | Low |
| 100 to 1,000 | 0.97 | > 260 °C | ≈ −50 °C | Low; the 350 cSt grade typically loses under 2% after 1 hour at 150 °C |
| 10,000 to 100,000 | 0.97 to 0.98 | > 260 °C | ≈ −40 to −50 °C | Lowest of the ladder |
Typical values — Certificate of Analysis governs. Refractive index sits near 1.40 and surface tension near 21 mN/m across the ladder. Values are compiled from published manufacturer technical data sheets cross-checked across four producers and reconciled to current RawSource product data; they are not a sales specification.
On flammability: every grade from 5 cSt upward has an open-cup flash point far above the 93 °C ceiling of the least severe GHS flammable-liquid category under the OSHA Hazard Communication Standard (29 CFR 1910.1200, Appendix B), and mid- and high-viscosity PDMS is reported on the grade SDS as not meeting GHS classification criteria. The volatile fluids below 5 cSt are a different case; check their own SDS.
Packaging follows the volume: 5-gallon pails for pilot lots, 55-gallon drums for production, 275-gallon IBC totes for mid-volume programs, and pallet, full-tote, or isotank quantities for continuous use. All straight PDMS grades classify under Harmonized System heading 3910.00 (silicones in primary forms); confirm the national tariff line and any shipment-specific transport classification for your destination.
The CoA covers viscosity at 25 °C, specific gravity, and appearance as standard; refractive index, acid number, and volatile content are reported where the grade’s specification includes them.
How to request a quote
To quote and ship the right grade the first time, send five things:
- Grade: the nominal centistoke value, or the duty if you want a recommendation.
- Specification: any limits your process holds beyond the standard CoA (viscosity tolerance, moisture, dielectric strength, volatile content).
- Volume and packaging: pails, drums, totes, or bulk, and whether this is a one-time lot or a recurring program.
- Application context: temperature range, contact materials, and whether the fluid will be near a painting or coating operation.
- Destination and timing: ship-to location and required date, so the quote reflects freight and stock position.
A sample of the candidate grade is the cheapest test you will run. Qualify it on your own equipment before committing a production volume, especially when choosing between two adjacent grades.
Methodology and sources
Grade-to-duty mappings come from RawSource’s per-viscosity product pages and viscosity guide, cross-checked against published manufacturer technical data sheets. Typical property values were compiled from four producers’ data sheets and reconciled to current RawSource product data, taking the more conservative figure where they differ; flash points are open-cup values.
Identity is anchored to the NIST WebBook and EPA CompTox entries for CAS 63148-62-9, the viscosity method to ASTM D445, and the flammability discussion to OSHA’s Hazard Communication Standard, Appendix B. Grade and question priorities come from RawSource’s Google Search Console data for the trailing 90 days. No producer or brand is named. Nothing here is a price, an offer, or a guarantee of availability.
Frequently asked questions
Who supplies silicone oil in bulk? RawSource supplies silicone oil (PDMS fluid) in bulk to industrial, formulation, and OEM buyers, in a viscosity ladder from 10 to 100,000 cSt, in pails, drums, and IBC totes, with a lot-specific CoA and SDS on every shipment. Send the grade, volume, and packaging for a quote against current stock.
Which silicone oil viscosity should I buy? Choose by duty: 10 to 100 cSt for spreading, carrier, and light lubrication; 350 cSt for general-purpose release, lubrication, and polishes; 1,000 cSt for higher-cling release and mechanical fluids; 5,000 to 100,000 cSt for damping, vibration control, and high-temperature antifoam bases. Sample the candidate grade before ordering at volume.
Is silicone oil flammable? Grades of 5 cSt and above have open-cup flash points from roughly 135 °C (5 cSt) to above 260 °C (50 cSt and up), well beyond the 93 °C cut-off for the least severe GHS flammable-liquid category. The volatile fluids below 5 cSt can be flammable and must be checked against their own SDS.
Is silicone oil the same as silicone fluid, PDMS, and dimethicone? Yes. All four names describe linear polydimethylsiloxane (CAS 63148-62-9; some grades list 9006-65-9). “Silicone oil” and “silicone fluid” are trade usage, “PDMS” is the chemical abbreviation, and “dimethicone” is the INCI name used in personal care. The centistoke figure is the viscosity grade, not a different substance.
How is bulk silicone oil packaged and classified for shipping? Standard packaging is 5-gallon pails, 55-gallon drums, and 275-gallon IBC totes, with pallet, full-tote, and isotank volumes on request. All straight PDMS grades fall under HS heading 3910.00. Mid- and high-viscosity grades are reported on their SDS as not GHS-classified; confirm transport status for your specific shipment against the grade SDS.
Can I use general-purpose 50 cSt silicone oil in a transformer? Not as a substitute for a transformer fluid. Transformer and fire-sensitive dielectric duty calls for the moisture-controlled silicone transformer oil supplied on an IEC 60836 / ASTM D 4652 basis with IEEE C57.111 acceptance testing. The general 50 cSt ladder grade is for release, lubrication, and non-critical insulating and heat-transfer use.
Editorial note. This page is general procurement and technical reference for industrial and professional buyers, not safety, regulatory, or formulation advice. Silicone oil here is an industrial PDMS fluid sold as a bulk raw material; nothing on this page is a cosmetic, medical, food-contact, or efficacy claim. Property values are typical reference figures, not a guaranteed specification; the Certificate of Analysis for the lot you purchase governs. Verify hazard, transport, and tariff classifications for your specific shipment, and always consult the current Safety Data Sheet (SDS) before handling. RawSource makes no warranty, express or implied, and assumes no liability for use of this information.
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