Sublimation often gets grouped alongside DTG, DTF, and screen printing as one of the "apparel printing methods," but it's actually more commonly and more effectively used on hard-surface, non-fabric products — mugs, metal water bottles, phone cases, puzzles, coasters — where it genuinely outperforms other methods rather than just being an apparel alternative.
The process works by turning dye into a gas under heat and pressure, which then bonds directly into a specially coated surface (rather than sitting on top of it as an ink layer would) — this is why sublimation requires products with a specific polyester or polymer coating, and why it doesn't work at all on plain, uncoated ceramic, glass, or metal without that specific coating already applied by the manufacturer.
For mugs specifically, this means the design becomes genuinely part of the mug's coated surface rather than a separate printed layer, which is why properly sublimated mugs tend to be dishwasher and microwave safe in a way that a mug with a vinyl decal or lower-quality print often isn't — the design simply can't peel or scratch off the way a surface-applied print potentially could.
File prep for sublimation on hard-surface products follows similar principles to apparel sublimation — high resolution (300 DPI at final size), and since there's no ink layer to soften edges, sharp, high-resolution source files matter more here than for more forgiving methods like DTG. Curved and wraparound products (mugs, tumblers) also require accounting for the physical wraparound the same way discussed for tumbler design elsewhere — a flat, front-facing design doesn't translate cleanly to a fully cylindrical printable surface.
For sellers already offering apparel designs, sublimated mugs, coasters, or phone cases are often one of the easier product-line expansions to make, since the same source artwork can frequently be repurposed with adjustments for the different print area, rather than requiring genuinely new design work — making it a reasonably low-effort way to diversify a catalog beyond apparel using assets you likely already have.