Conventional sheet-fed offset ink dries through oxidation, a slow chemical process. When sheets land in the delivery pile at production speed, the printed surface of one sheet sits flat against the back of the next, and wet ink transfers upward. That transfer is called set-off, and offset spray powder is the one consumable that reliably prevents it in commercial offset work.
An anti-set-off spray powder is applied in a timed pulse as each sheet exits the last printing unit. The particles land on the ink film, stand the next sheet off by a few micrometers, and leave an air channel around the pile so oxygen can reach the ink. The powder itself is almost always a natural starch (corn, potato, tapioca, rice, or wheat) sized to match the stock you are running. It is a mechanical spacer, not a drier or an ink additive, that buys the ink the time it needs to set.
Coated vs. Uncoated Spray Powder: How to Choose
Every powder on this page is either coated or uncoated, and the distinction changes how the powder flows through your applicator and how it behaves downstream.
A coated spray powder, such as the Varn Coated 230 or Press Smart Coated grades, is encapsulated with a micro-thin natural coating. That coating helps particles flow freely through spray guns, resists moisture pickup, and lays a uniform film across the sheet. Coated powders are the default for high-speed perfecting presses, electrostatic applicators, and any job that demands tight spray-pattern control or deep stacking.
An uncoated spray powder, such as the OMC 320, 326, 332, 435, and 440 range or Varn Uncoated 50, is pure food-grade starch. Uncoated grades are cost-effective and are the correct choice for multi-pass work and for sheets that will be foil-stamped or laminated downstream, where a silicone-coated powder could interfere with adhesion at the finishing station. When in doubt about your postpress sequence, default to uncoated.
Choosing the Right Micron Size for Your Stock
Particle size is the other critical variable. The correct diameter of anti offset powder depends on substrate weight, ink film thickness, and delivery pile height. As a starting guide:
- Fine grades (roughly 15 to 20 micron) suit text-weight and lightly coated stocks around 150 gsm.
- Medium grades (25 to 35 micron) cover most label, carton, and mid-weight cover stocks.
- Coarse grades (40 micron and up) are built for heavy board, folding carton, and non-absorbent substrates.
Apply the minimum amount of powder that actually prevents set-off. Over-spraying is not a safeguard. Too much powder builds up on impression cylinders, fouls blankets, causes piling, and creates problems at coating, laminating, and foil-stamping stations downstream. If you keep finding residual powder on finished work, the fix is usually a smaller particle size plus a lower spray rate, not a different brand. For routine press maintenance, we also stock plate cleaners and cotton wipes and shop cloths sized for pressroom volume.
Brands and Sizes We Stock
Our 36-SKU spray powders range covers Heidelberg, Komori, Ryobi, and smaller duplicators with the micron grades and container sizes your applicator is built for. Varn for Coated 230 and Regular 23 grades in 11 lb and 44 lb cartons, plus Uncoated 50 for heavier board. OMC for the full uncoated micron ladder: 320 (20μ), 326 (26μ), 332 (32μ), 435 (35μ), and 440 (40μ), in 25 lb and 50 lb cartons. Allied Press Smart for 25 micron coated in 1 kilo bags, a practical size for short-run shops. If you need a grade that is not listed, call us. We regularly source discontinued or special-order formulations direct from the manufacturer.
Keep containers sealed between shifts, store at room temperature in a dry area, and keep applicator lines clean to maintain a consistent spray pattern and extend shelf life. For operator comfort during change-overs, we also carry nitrile gloves and Big Blue shop wipes.
Ordering and Shipping
Most orders on this page ship the same or next day via UPS Ground to the 48 contiguous states. Alaska, Hawaii, and Canada require a direct shipping quote, and we will ship to a U.S.-based freight forwarder for customers outside the country. Free shipping applies to all items over $50.
Cartons are packed to protect the powder in transit, and your order is tracked from our warehouse to your dock. If you are setting up a full pressroom consumables program, you can build the spray powder order alongside everything else in our pressroom supplies range and receive one consolidated shipment. Technical questions are welcome before the order goes in, and on-site support is available when the situation calls for it.
If you have been running a specific Varn, OMC, Allied, or Nikken part number for years, send us the SKU and we will confirm stock and cross-reference a current-production equivalent before you place the order.
Anti Set Off Powder Frequently Asked Questions
