Screen Printing Underbase, 9 Tips on how to do

Vibrant colors on dark garments, crisp details, and durable prints — all of that begins beneath the actual artwork: with the underbase.

Many printers underestimate this first layer of ink. Yet it often determines whether a print shines with real brilliance or disappears into the fabric. In this comprehensive guide, you’ll learn:

• What an underbase is — and why you need it
• Common mistakes and misconceptions
• 9 proven, practical pro tips
• Bonus know-how on flashing, pallet temperature, and tools
• How underbase technology has evolved and where it is heading

What Is an Underbase? (And Why Is It So Important?)

An underbase — also called underlay, undercoat, or “base white” — is a bright first layer, usually white, printed before all other colors.

It works like a primer and ensures that:

• Colors aren’t absorbed by the fabric
• Brightness and intensity of the top colors remain intact
• Fine details are reproduced cleanly
• Dye migration (especially on polyester) is reduced
• Colors on dark shirts look the way they’re supposed to

In short: without an underbase, yellow on black becomes a dirty ochre — not yellow.

A Look Back: How the Underbase Revolutionized Screen Printing

In the early days of textile printing, printers used extremely thick ink layers to make colors visible on dark fabrics. That changed with the introduction of:

• Multicolor carousels
• Flash-cure units
• Automatic printing presses

These innovations made professional underbase printing possible. Today, the underbase is standard in high-quality textile printing and the foundation for modern hybrid, simulated process, and CMYK techniques.

Common Misconceptions About Underbases

Myth 1: “The underbase white is the highlight white.”
→ Wrong.
The underbase is your foundation. The highlight white on top creates the real “pop.”

Myth 2: “Underbases are always white.”
→ Not true.
Depending on the design, gray, beige, or clear bases can work better.

Myth 3: “One mesh count works for everything.”
→ Incorrect.
The ideal mesh depends on the artwork, ink type, and desired ink deposit.

Myth 4: “More underbase = better.”
→ Too much underbase makes the print thick and rubbery.

The 9 Most Important Tips for Perfect Screen-Printing Underbases

Here are the key technical factors — clearly explained and ready to apply.

1. Know When You Actually Need an Underbase

Use an underbase for:

• Dark garments
• Bright, vibrant colors
• Photographic or detailed designs
• Designs that would look dull or gray without a base

Soft vintage looks intentionally use little or no underbase.

2. Choose the Right White Ink

For underbases, use:

• High-opacity white
• Fast-gelling / Flash white for PFP printing
• Low-bleed white for polyester and blends

Underbase white ≠ highlight white.
They serve different purposes.

3. Use the Correct Mesh Count

For strong, solid underbases:

• Manual: 110–156 (43 t/cm – 61 t/cm)
• Automatic: 156–190 (61 t/cm – 75 t/cm)

For detailed or halftone underbases:

• Manual: 180–230 (71 t/cm – 90 t/cm)
• Automatic: 200–260 (79 t/cm – 102 t/cm)

Tip: Use mid-thread-diameter meshes (e.g., S-Mesh, LX-Mesh) for optimal ink laydown.

4. Correct Emulsion Over Mesh (EOM)

Ideal for underbases:

• At least 10% EOM

Benefits:

• Even ink deposit
• Clean edges
• Smooth base for top colors

5. Squeegee Selection and Pressure

• Softer squeegees = more ink
• Harder squeegees (70–75 durometer) = more control
• Round-edge squeegees for water-based or thick underbases

Pressure rule:

Use only the pressure you need
→ Ink should sit on top, not be pushed through the shirt.

Test:
Visible white on the inside of the shirt = too much pressure.

6. Adjust Your Print Speed

• Water-based inks → faster printing
• Plastisol → medium speed

Goal: shear the ink cleanly, not force it through the mesh.

7. Set Your Off-Contact Correctly

Standard: 1 mm

Important: evenly across the whole screen.

• Hoodies → slightly more off-contact

Uneven off-contact = uneven white areas.

8. Ensure Proper Screen Tension

• Minimum: 20 N/cm
• Even tension in all four directions

Uneven tension → blotchy underbases → fuzzy edges.

9. Choke the Underbase Properly

The underbase should be slightly smaller than the top colors:

• Prevents white from “peeking out”
• Usually 1–3 pixels / 0.2–0.4 mm

In simulated process or complex designs, the underbase may be:

• Halftoned
• Grayscale
• Software-generated (T-Seps, UltraSeps, AccuRIP Black Pearl)

Bonus Tips: Master Flashing & Pallet Temperature

Do NOT over-flash!

Goal:

• Gel the ink, don’t fully cure it
• Surface should be slightly tacky, not hot

Over-flashing leads to:

• Poor ink adhesion
• Excess heat on the pallet
• Screen clogging
• Thick, heavy prints

Keep Pallet Temperature Low

If pallets get too hot:

• Ink dries in the screen
• Water-based inks react very sensitively
• Prints become inconsistent

Solution: monitor temperature.

An infrared thermometer is essential to check:

• Pallet temperature
• Flash temperature
• Heat press settings
• Lycra/heat-sensitive fabrics
• Shirt preheating

Tip:
IR guns measure surface, not the ink core temperature.
For true ink curing, use a donut probe (donut thermometer).

The Future of Underbase Printing

Emerging developments include:

• Hybrid printing (screen underbase + digital colors)
• 3D underbases for high-density effects
• CTS automation
• Fast-curing inks
• Eco-friendly alternatives (water-based, eco-plastisol)
• UV-LED curing

The underbase continues to evolve — becoming smarter, faster, and more precise.

Conclusion: The Underbase Is the Foundation of Brilliant Prints

A perfect underbase is:

• Cleanly built
• Technically precise
• Accurately registered
• Flashed correctly
• Not too thick
• Not overheated
• Not undercured
• Properly choked
• Fully cured (verified!)

Master the underbase — and you’ll produce prints that shine, last, and look truly professional.