If you've ever watched a crisp, custom screen print peel off a wooden coaster after one wash, or seen ink bead up and refuse to stick to a glass beer mug mid-run, you know the frustration of printing on unconventional surfaces. I learned this lesson the hard way last year when I agreed to print 200 branded wood coasters for a local café: I used my go-to t-shirt plastisol ink setup, skipped all surface prep, and walked away with 180 useless, peeling coasters and a $300 loss. After months of testing, tweaking, and wasting far too much ink and scrap material, I've cracked the process for consistent, durable prints on both wood and glass---no fancy lab equipment or upgraded press required. Whether you're expanding your print shop offerings or making custom merch for your own brand, these techniques will cut your rework rate to zero.
Prep Is 90% of the Battle (And It Varies Wildly by Material)
The biggest mistake I see new printers make with wood and glass is treating them like fabric: they slap a screen down and pull a squeegee without any surface prep, then wonder why the ink falls off 10 minutes later. Both materials require targeted prep to give ink something to grip, and the steps are totally different for each. For wood, start by identifying if your piece is raw, unfinished, or pre-finished with stain/varnish. If it has a pre-existing sealed finish, you'll need to sand it down to the raw wood layer first---ink will never adhere to a varnished or stained surface. For raw wood, you have two path options depending on the look you want: for a vintage, "soaked in" design, skip sealing, just sand the surface lightly with 220-grit sandpaper to remove loose splinters, wipe it down with 99% isopropyl alcohol (IPA) to remove dust, and you're ready to print. For crisp, opaque prints that won't fade or bleed over time, seal the raw wood first with a clear, water-based polyurethane or acrylic sealer, let it cure for 24 hours, then sand lightly with 320-grit sandpaper to create a rough texture for the ink to grip. When coating your screens for wood prints, use a 200--300 micron emulsion layer (thinner than the 400+ micron you'd use for heavy plastisol on fabric) to get razor-sharp stencil edges with no fuzzy halation around fine lines. Glass prep is even more strict, because even a tiny fingerprint or factory dust coating will make ink bead up and refuse to stick. Wipe every piece of glass with 99% IPA, let it dry completely, then wipe it again with a lint-free microfiber cloth to remove any remaining residue. Frosted or etched glass has a natural rough texture that helps ink adhere, but you still need to degrease it first to remove factory coatings. For smooth, clear or tinted glass, there's no need to sand---just make sure it's 100% grease-free before you print.
Pick the Right Ink for Your Material (Your Standard Tee Ink Won't Cut It)
Standard plastisol ink works great for cotton and polyester, but it's formulated to fuse to fabric fibers, not hard, non-porous surfaces. For wood, your best bets are water-based polyurethane ink or UV-curable ink. Water-based ink penetrates raw wood pores beautifully for that vintage, hand-painted look, and stays flexible enough to avoid cracking as wood expands and contracts with humidity changes. For sealed wood or pieces that will see heavy use (like cutting boards or coasters), UV ink is the way to go: it cures instantly into a rock-hard, scratch-resistant layer that won't peel even with repeated washing. If you're printing on dark wood, lay down a thin white underbase first, cure it, then print your color layers on top---otherwise your design will look muddy and unreadable. A quick pro hack for porous raw wood: add 1 teaspoon of fabric softener per gallon of water-based ink to help it flow into the wood pores without bleeding into adjacent design elements. For glass, you have two reliable options: UV-curable glass ink, or solvent-based glass ink. UV ink bonds permanently to glass, cures in 10--15 seconds under a UV lamp, and is fully dishwasher safe---perfect for drinkware, wedding favors, or decorative pieces that will see regular use. Solvent-based ink is a cheaper alternative for smaller shops, but it requires better ventilation, takes longer to cure, and is less durable than UV ink for pieces that will be washed often. Avoid standard plastisol for glass entirely unless you're only making decorative pieces that will never be exposed to water or heat: it will peel off in a single dishwasher cycle. For tinted or dark glass, a white underbase is non-negotiable to make your design pop, just like with dark wood.
Printing and Curing Techniques That Guarantee Adhesion
Even with perfect prep and ink, bad printing technique will leave you with smudged, blurry prints. For both materials, adjust your squeegee setup to match the surface: use a 70--80 durometer squeegee for wood (softer than the 90 durometer you use for tees) to conform to the slight unevenness of the wood surface, and press with slightly more pressure than you would for fabric, but not so hard you dig into the wood or push ink past the edges of your stencil. For glass, use an even softer 60--70 durometer squeegee to push ink evenly across the smooth surface without scraping it off mid-pull. If you're printing on curved surfaces (round wood cutting boards, curved glass mugs), use a low-profile screen frame that sits flush against the curve, and a flexible squeegee blade that contours to the shape to avoid gaps where ink will bleed through. Curing is just as important as printing for both materials. For water-based wood prints, cure at 320°F (160°C) for 3 minutes in a conveyor dryer, or let them air cure for 24 hours if you don't have a dryer. For UV wood ink, cure for 30 seconds under a UV lamp. For glass, UV ink only needs 10--15 seconds of exposure to a 365nm UV lamp to bond permanently---no heat required. Solvent-based glass ink needs to cure at 250°F (120°C) for 2 minutes. A critical rule for both materials: don't touch or pack the prints for 24 hours after curing, even if they feel dry to the touch. The bond is still setting during that time, and handling them early will cause smudging or peeling.
Avoid These Common (and Costly) Mistakes
After wasting hundreds of dollars on failed runs, I've learned to watch out for these four traps:
- Skipping the test swatch: Even if you've printed on the exact same type of wood or glass before, every batch has slight variations in finish, porosity, or coatings that can affect adhesion. Always print a test swatch on a scrap piece of your material before running a full order.
- Over-curing your prints: Over-curing water-based wood ink makes it brittle and prone to cracking as the wood expands and contracts; over-curing UV glass ink can cause it to yellow and peel. Stick to the recommended curing times, and use a temperature gun to check your dryer or lamp output if you're unsure.
- Using the wrong emulsion thickness: Thick, heavy emulsion works for heavy plastisol on fabric, but it creates fuzzy stencil edges on wood and glass, blurring fine details. Stick to 200--300 micron emulsion for these materials to get crisp, clean edges.
- Ignoring expansion gaps on wood: Wood expands and contracts with humidity and temperature changes, so if you're printing on small pieces like coasters or ornaments, leave a 1/16 inch gap between the edge of your design and the edge of the wood. If the design touches the edge, the ink will crack as the wood swells.
Quick Troubleshooting for Common Failures
If you're running into unexpected issues, run through this fast checklist first:
- Ink is beading up and not sticking: You skipped the degreasing step for glass, or didn't sand/seal the wood properly. Wipe the piece with IPA again, or sand and reseal the wood, then reprint.
- Design is bleeding or blurry: Your emulsion is too thick, you're using too much pressure with the squeegee, or your screen tension is too loose. Thin your emulsion, reduce squeegee pressure, or retension your screen.
- Print is peeling after curing: You used the wrong ink for the material, or under-cured the print. Switch to a material-specific ink, or increase your curing time/temperature by 10% and test again.
- Design looks muddy on dark wood/glass: You forgot the white underbase. Lay down a thin white layer, cure it fully, then print your color layers on top.
At the end of the day, printing on unconventional materials is all about embracing trial and error, and leaning into the unique textures of each surface. There's nothing quite like the look of a custom screen print on raw, grainy wood, or the glossy, permanent finish of a UV-cured glass mug---these are products you can't make with standard fabric printing, and they command a 2--3x markup over basic tees and totes. The first time I pulled a perfect, peel-free wood coaster off the press after months of tweaking, I knew all the wasted material was worth it. Now I offer custom wood and glass prints as 40% of my shop's revenue, and I'm constantly finding new surfaces to experiment with: slate coasters, ceramic tiles, even acrylic phone cases. All it takes is a little extra prep, the right ink, and a willingness to test on scrap pieces before you run a full order.