When you're setting up a screen‑printing job, the squeegee is the workhorse that determines how well the ink transfers from the screen to the product. While mesh count, screen tension, and ink viscosity often get the spotlight, squeegee hardness is equally critical. Pick the wrong durometer and you'll see streaks, uneven coverage, or premature wear on your screens.
Below is a practical guide to matching squeegee hardness with ink chemistry and substrate characteristics, so you can achieve consistent, high‑quality prints every time.
Understanding Squeegee Hardness
| Durometer (A) | Typical Description | Flexibility | Common Uses |
|---|---|---|---|
| 40‑50A | Very soft, rubbery | Highly flexible, bends easily | Thin, delicate films; low‑viscosity inks |
| 60‑70A | Soft | Good "give" for uneven surfaces | Water‑based inks on coated paper, flexible PVC |
| 80‑90A | Medium‑soft | Balanced rigidity/flexibility | General purpose; most solvent inks on smooth substrates |
| 100‑110A | Medium‑hard | Stiff enough for high‑viscosity inks | Plastisol on textiles, thick UV inks |
| 120‑130A | Hard | Very stiff, minimal flex | Heavy‑duty coatings, metal substrates, high‑mesh screens |
Durometer numbers follow the Shore A scale; higher numbers = harder (less flexible).
Ink Types & Their Demands
| Ink Type | Viscosity (cP) | Typical Substrates | Recommended Hardness Range |
|---|---|---|---|
| Water‑Based | 800‑2,500 | Paper, cardboard, thin film | 50‑80A |
| Solvent | 1,200‑3,500 | Vinyl, PET, metal, glass | 70‑100A |
| UV Curable | 1,500‑4,500 | Rigid plastics, metal, wood | 80‑120A |
| Plastisol | 3,500‑6,500 | Textiles, canvas, thick coatings | 100‑130A |
| Hybrid (e‑Coat, Low‑Solvent) | 1,000‑2,800 | Flexible packaging, laminates | 60‑100A |
Viscosity is a guiding factor: higher viscosity inks need a harder squeegee to push the thicker fluid through the mesh.
Substrate Characteristics That Influence Hardness Choice
| Substrate Feature | Effect on Ink Transfer | Squeegee Hardness Tips |
|---|---|---|
| Surface Roughness (e.g., corrugated board) | Ink can pool in valleys → need more pressure | Harder squeegee (100‑130A) to apply consistent force |
| Flexibility (e.g., stretch film) | Substrate may deform under pressure | Softer squeegee (50‑70A) to avoid "spring‑back" and ghosting |
| Porosity (e.g., uncoated paper) | Ink can be absorbed quickly → risk of drying in the screen | Medium‑soft (70‑90A) for smoother release |
| Thermal Sensitivity (e.g., heat‑shrink films) | Excess heat from friction can warp | Softer squeegee + lower off‑contact pressure to reduce heat build‑up |
| Thickness (e.g., metal plates, ½" wood) | Requires more energy to wet surface | Harder squeegee (120A+) and higher off‑contact angle |
Decision‑Making Flowchart (Text Version)
-
Identify Ink Viscosity
- Low < 1,500 cP → start with 50‑70A
- Medium 1,500‑3,500 cP → 70‑100A
- High > 3,500 cP → 100A+
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Assess Substrate Roughness
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Consider Substrate Flexibility
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Check Mesh Count
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Test & Adjust
Practical Tips for Real‑World Set‑ups
5.1. Off‑Contact Angle Matters
Even with the perfect durometer, an improper off‑contact angle will sabotage the print.
- Soft blade: 30‑45° off‑contact to allow flexing.
- Hard blade: 10‑20° off‑contact for more direct pressure.
5.2. Pressure & Speed Balance
- Higher pressure can compensate for a softer blade but risks screen wear.
- Faster stroke favors harder blades; slower strokes give soft blades more time to push ink.
5.3. Blade Edge Geometry
- Rounded (R‑3 to R‑5) edges reduce drag on delicate substrates.
- Square edges give sharper deposit on rigid surfaces but can gouge softer films.
5.4. Maintenance Checklist
- Inspect wear every 8‑10 hrs of print time. Hard blades can become "glassy" and lose flexibility.
- Clean after each job ---ink buildup on the edge changes effective hardness.
- Rotate blades in your set; always have at least two durometers on hand for quick swaps.
5.5. Environmental Considerations
- High humidity thickens water‑based inks → shift toward a harder blade.
- Cold workshops thin solvent inks → a softer blade may improve coverage.
Sample Set‑ups for Common Applications
| Application | Ink | Substrate | Mesh | Recommended Squeegee |
|---|---|---|---|---|
| T‑shirt printing | Plastisol | 100% cotton | 110 T | 120‑130A, square edge, 10° off‑contact |
| Flexible PVC signage | Solvent | 0.5 mm PVC | 156 T | 80‑90A, rounded edge, 30° off‑contact |
| Corrugated cardboard packaging | Water‑based | White corrugated | 230 T | 100A, square edge, 20° off‑contact |
| Metal nameplates | UV curable | Anodized aluminum | 110 T | 100‑120A, square edge, 15° off‑contact |
| Reusable shopping bags | Hybrid low‑solvent | Non‑woven polypropylene | 156 T | 70‑80A, rounded edge, 30° off‑contact |
Quick Reference Cheat Sheet
- Very Soft (40‑50A) -- Thin, low‑viscosity inks + highly flexible substrates.
- Soft (60‑70A) -- Water‑based on smooth paper, low‑solvent on flexible film.
- Medium‑Soft (80‑90A) -- General purpose; most solvent inks on moderate surfaces.
- Medium‑Hard (100‑110A) -- Plastisol, thick UV, heavy‑weight textiles, rough substrates.
- Hard (120‑130A) -- High‑viscosity UV, metal, thick coatings, high‑mesh screens.
Bottom Line
Choosing the right squeegee hardness isn't a one‑size‑fits‑all decision---it's a balancing act between ink viscosity , substrate texture , and operational parameters like mesh count and printing speed. By systematically evaluating each factor and using the durometer ranges outlined above, you'll reduce trial‑and‑error, extend the life of your screens, and deliver prints that meet the highest quality standards.
Happy printing!