Screen Printing Exposure Time Chart & Step Test

Home › Screen Printing › Screen Printing Exposure Time: How Long to Expose a Screen

Quick answer: There is no single exposure time for every screen. As a starting point, a fast SBQ (photopolymer) emulsion on an LED exposure unit usually needs seconds to about a minute, a diazo or dual-cure emulsion under the same light takes several times longer, and a halogen work light or sunlight takes minutes. The exact time depends on your emulsion, mesh count and color, coating thickness and light source, so find yours with a step-wedge test and write it down.

Starting exposure times by light source

Use these only as a first guess for a step test. Your emulsion's data sheet and your own test beat any chart.

Light source	Fast SBQ / photopolymer emulsion	Diazo or dual-cure emulsion	Notes
LED exposure unit (purpose-built)	About 10–60 seconds	About 1–4 minutes	Most consistent; vacuum or weighted glass keeps film tight
Metal halide / UV point light	About 30–90 seconds	About 2–6 minutes	Distance changes time a lot; keep it fixed
UV fluorescent tube unit	About 1–3 minutes	About 5–12 minutes	Tubes weaken with age; re-test as they fade
500 W halogen work light (12–18 in. away)	About 3–8 minutes	About 8–15 minutes	Hot and uneven; hobby use only
250 W / 150 W bulbs	Longer than 500 W; test	Much longer; test	Low output makes undercuring likely
Direct sunlight	About 30 seconds – 2 minutes	About 1–5 minutes	Changes with time of day, season and clouds

These ranges are general shop starting points, not maker specifications. Always check the emulsion's own instructions.

What changes your exposure time

Emulsion type — SBQ photopolymers such as Ulano QX-5 SBQ photopolymer emulsion, quart ($32.00) and Ulano TRIFECTA SBQ photopolymer emulsion, gallon ($70.00) are made to expose fast. Diazo and dual-cure emulsions such as Ulano 925WR-P water-resistant emulsion need longer but are built for durability and water resistance. See how to choose emulsion.
Coating thickness — more coats on the squeegee side mean a thicker stencil and a longer exposure. Coat the same way every time with a scoop coater.
Mesh count and color — low mesh counts hold more emulsion and need more time; yellow (dyed) mesh cuts light scatter but also lengthens exposure. See the mesh count chart.
Light source and distance — doubling the distance from a point light cuts the light reaching the screen to about a quarter.
Film positive density — a weak, see-through film lets light leak through, so detail closes up. Use a dense black positive on waterproof inkjet film.
Dryness of the screen — a damp coat never hardens fully, whatever time you use.

How to find your exact exposure time (step test)

Coat and dry a test screen exactly the way you coat production screens.
Lay a step-wedge film such as the Chromaline 10-Step Exposure Guide ($14.95) — or the Chromaline Exposure Calculator ($44.95) — on the print side, with a film that has fine lines and halftones.
Expose for about double your best guess. The guide gives each section a different share of that light, so one exposure shows you several times at once.
Wash out gently, let it dry, and look for the step where the emulsion is fully hardened (no slimy feel, color matches the cured coat) and fine detail still opens cleanly.
Work out the time for that step, then write it on the wall next to the unit with the emulsion, mesh and coat count.
Re-test when you change emulsion, mesh, coating method or bulbs.

Underexposed or overexposed?

Sign	Likely cause	Fix
Emulsion feels slimy, washes off in sheets, or breaks down on press	Underexposed	Add time (or move the light closer); make sure the coat was fully dry
Fine lines and halftones will not wash out	Overexposed or light undercutting the film	Cut time; use a denser positive; get better film-to-screen contact
Edges of the image are jagged or soft	Poor contact or light scatter	Use glass or vacuum; try dyed (yellow) mesh for fine detail
Pinholes after exposure	Dust or a thin coat	Clean glass and film; coat evenly; block out with tape or blockout

Exposure units and emulsions we stock

Chromaline Quick Image LED Exposure Unit 26" x 31" ($2,625.00) — LED unit for frames up to 26" x 31". Compare units on our screen printing exposure unit guide.
Ulano QX-5 SBQ photopolymer emulsion, quart ($32.00) · Ulano TRIFECTA SBQ photopolymer emulsion, gallon ($70.00) · Ulano Orange pre-sensitized SBQ emulsion, quart ($23.00) · Ulano 925WR-P water-resistant emulsion
Chromaline 10-Step Exposure Guide ($14.95) · Chromaline Exposure Calculator ($44.95)

New to burning screens? Start with how to make a screen for screen printing, then how to clean and reclaim screens.

Prices are today's web prices and can change. Product names and types are from the makers as shown on our product pages.

Frequently asked questions

How long do you expose a silk screen?

It depends on the emulsion and light. A fast SBQ emulsion on an LED exposure unit often needs about 10–60 seconds; diazo or dual-cure emulsions take a few minutes; a halogen work light takes several minutes. Confirm with a step test.

How long should I expose emulsion with a 500 watt halogen light?

A common starting range is about 3–8 minutes for a fast SBQ emulsion and 8–15 minutes for diazo or dual-cure, with the light 12–18 inches away. Halogen output is uneven, so run a step test.

How long do you expose a screen in the sun?

Often 30 seconds to 2 minutes for fast photopolymer emulsion and 1–5 minutes for diazo, but sunlight changes all day. Test on a scrap screen first.

How do you calculate exposure time for screen printing?

Use a step-wedge test such as the Chromaline 10-Step Exposure Guide or Exposure Calculator: expose once at about double your guess, find the step that is fully hardened but still holds detail, and use that time.

What happens if a screen is underexposed?

The emulsion stays soft, can feel slimy, washes away during washout, and breaks down on press. Add exposure time and make sure the coat is fully dry before exposing.

Does mesh count change exposure time?

Yes. Lower mesh counts hold a thicker layer of emulsion and need more time; dyed (yellow) mesh also needs more time than white mesh.

Does Buckets of Ink burn screens for customers?

No. We sell the emulsions, films, exposure guides and exposure units and help you dial in your own times. Call 480-229-7806.

Need help dialing in exposure? Call us.
Buckets of Ink is a screen printing supply house and equipment dealer in Tempe, Arizona. Ask about our discounts, starter packages and great financing on equipment — we'll help you get into your next machine.
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Call 480-229-7806 · Showroom & pickup: 906 S Priest Dr, Suite 101, Tempe AZ 85281 · In-stock orders placed by 2:30 PM Arizona time ship the same day · Free ground shipping on orders over $500 (equipment excluded; see shipping and returns).