Laser cutting stencils is one of the easiest ways to turn a hobby laser into steady income, because reusable stencils for signs, cakes, walls, and crafts sell year-round. The short answer to "what should I use and how should I cut it": 7.5 to 10 mil mylar (that is a thin polyester film, roughly 0.19 to 0.25 mm thick) is the sweet spot for almost every paint stencil, and you want just enough laser power to cut through cleanly while letting the melted edges seal themselves smooth. This guide walks through the right film, the settings that keep edges from fraying, and the design tricks that make a stencil survive dozens of paint jobs instead of falling apart after three.

Why 7.5 to 10 mil mylar is the stencil sweet spot

Mylar comes in several thicknesses, and the number on the box matters more than most buyers expect. A "mil" is one thousandth of an inch, so 7.5 mil film is about 0.19 mm and 10 mil is about 0.25 mm. Thinner film (5 mil and below) cuts fast and lays flat on slightly curved surfaces, but it tears when you peel dried paint off it and it curls after the first wash. Thicker film (14 mil and up) feels sturdy like a credit card, but it does not sit tight against wood grain, so paint bleeds under the edges and ruins the crisp look customers pay for.

The middle range wins because it balances three things at once: it is thick enough to block paint and survive handling, thin enough to lie flat on boards and walls, and it cuts in one pass on even a modest 40W CO2 machine. If you only stock one film, make it 10 mil. Add a roll of 7.5 mil for fine lettering and detailed work where the cut lines are small, and you are covered for nearly every stencil order that comes in. Food-safe grades exist too, which matters if you sell cake or cookie stencils and want to advertise that honestly.

Laser settings that seal mylar edges

Mylar is a polyester, and polyester melts. That sounds like a problem, but it is actually the reason laser-cut stencils outlast hand-cut ones: if your settings are right, the laser slightly melts the cut edge and seals it into a smooth, hard rim. Sealed edges resist paint buildup, wipe clean easily, and never fray into fuzzy threads that ruin the next paint job.

Start from these proven starting points on a 40-50W CO2 machine with 10 mil mylar, then adjust for your own machine:

• Speed 15-20 mm/s, power 25-35%, for clean through-cuts with a light seal.
• Speed 8-12 mm/s, power 20-25%, if you see browning and want a cooler cut.
• Air assist (a small air jet that blows across the cut point) set low. Some airflow keeps smoke off the film, but too much pressure distorts the thin sheet while cutting.

Three symptoms tell you how to adjust. If the edges are fuzzy and lightly stuck with melt-blobs, your power is too high or speed too slow; reduce power by 5% and retest. If the film cuts in some spots but not others, or you have to run the job twice, your power is too low; raise it in small steps. If the cut line looks dark brown and brittle, the film is burning rather than melting, so increase speed before you touch anything else. Run every test on a scrap corner, because a two-minute test piece saves you a whole wasted sheet.

Bridge and letter design that holds together

A stencil is only as strong as its weakest connection — every island of material you remove has to be held in place by bridges, which are the small uncut sections that connect the design to the surrounding sheet. Skip the bridges and the middles of your letters fall out on the cutting bed, and the stencil paints as a blob. Design them deliberately instead of letting software place them at random.

For lettering, use fonts built for stencils (search "stencil font" — these come with gaps already designed in) or add your own breaks. A good rule of thumb: bridges should be 2-3 mm wide on 10 mil film, and every letter should have at least one. On popular letter sizes (letters 25-50 mm tall), two bridges per letter keeps everything straight through repeated painting. The exception is script fonts, which connect letters naturally; there you only need to break long enclosed shapes like the loop of a capital B.

Think about paint flow too. Sharp inside corners collect stress and tear first, so round every inside corner to at least 1 mm radius in your design software. Keep the smallest cut slot above 1.5 mm wide, because slots narrower than that clog with paint and are nearly impossible to clean. If a customer's design forces tiny details, quote it on 7.5 mil film, which holds finer detail than 10 mil simply because there is less material to push a cut through.

Cleaning and reuse life

How long a stencil survives depends far more on how the customer cleans it than on how you cut it. Paint left to dry on film is the main killer: once acrylic paint cures in a fine slot, no amount of soaking removes it cleanly, and the stencil tears when someone picks at it. The good news is that proper care is simple, and you can print a small care card to include with every order — customers appreciate it, and it cuts your refund rate.

The care routine worth printing: wipe or rinse the stencil before the paint dries, use cool water with a little dish soap, lay it flat on a towel to dry, and store it flat between two pieces of cardboard. Never scrub with anything rough, never fold it, and never clean it with strong solvents, which cloud and stiffen the film. With that routine, a 10 mil mylar stencil routinely survives 30-50 uses for water-based paints and more for occasional use.

Sell the durability honestly. Market-grade customers (sign painters, furniture refinishers) will happily pay more for a stencil rated for dozens of uses, and your product photos can show a used stencil next to a fresh one to prove the claim. If you offer both, say so in the listing: "hobby grade" single-use cardstock at a low price and "pro grade" mylar built for reuse covers both kinds of buyers without discounting the film product.

How to cut a reusable lettering stencil

Follow these steps from file to finished, sellable stencil:

1. Pick the film. Put 10 mil mylar on the bed shiny side up, and wipe the surface with a dry cloth so dust does not block the laser.
2. Set up the design. Open your design file, set the art to actual size, and check that every enclosed shape has a bridge of 2-3 mm. Round inside corners to 1 mm or more.
3. Choose the right cut mode. Use vector cutting (the machine follows the outline path) rather than engraving mode, because a cut must go fully through the film.
4. Enter starting settings. For 10 mil film on a 40-50W CO2 machine: speed around 15 mm/s and power around 30%, with low air assist on.
5. Run a corner test. Cut a small square of the design in a scrap corner first. Look for a clean edge with a slight glossy seal and no browning.
6. Adjust and cut the full sheet. If the test cut did not go through, add 3-5% power. If it browned, add speed. Then run the full job.
7. Remove and inspect. Peel the film gently, pop the waste out of the letters with a fingernail, and hold the stencil up to a light to spot any uncut threads, which you can clear with a sharp craft knife.
8. Flatten and pack. If the film curled from heat, press it flat under a book for an hour. Then bag it flat with your care card and it is ready to ship.

Common questions (FAQ)

What material is best for laser cut stencils?

Mylar polyester film is the best all-around choice because it cuts cleanly, seals its own edges under the laser, washes clean, and bends without cracking. Acetate is cheaper but grows brittle and curls, and cardstock works only for single-use projects. For food-contact stencils, buy a food-safe grade of mylar.

How thick should mylar be for stencils?

Use 7.5 to 10 mil mylar for most reusable stencils. The 10 mil thickness handles rough handling and repeated washing, while 7.5 mil suits fine lettering and small details. Save 5 mil for flexible curved surfaces and 14 mil for large, simple shapes on flat walls.

Why do my stencil edges melt?

Some melt is good — a light melt seals the edge smooth. If you see heavy blobs, curling, or brown burnt edges, your power is too high or your speed too slow for the film thickness. Lower the power in 5% steps, raise the speed, and keep air assist gentle so the thin sheet does not lift off the bed mid-cut.

Related reading

A reliable CO2 machine is what makes stencil work repeatable, since sealed edges and clean fine detail depend on stable power and good motion control. If you are comparing machines for a small stencil or craft business, the overview of laser cutter types and power classes at https://www.hflaser.com/laser-cutter.html is a useful plain-English reference for matching machine specs to the materials you plan to sell.