Flexo plate hardness describes how strongly a finished photopolymer plate resists indentation. Suppliers usually report it as Shore A durometer. The number is useful, but it is not a stand-alone quality grade and there is no universal hardness that fits every flexo job.
Plate family, gauge, processing, substrate, image content, mounting tape, and press condition work together. A useful specification therefore says more than “use a hard plate.” It identifies the exact plate construction and the print condition it was approved for.
Shore A is a plate specification, not a universal target
Supplier data shows why one default number is misleading. DuPont lists its Cyrel DPI hard-durometer plate at 76 Shore A for the 0.045-inch gauge and 70 Shore A for the 0.067-inch gauge. Its Cyrel DFS medium-hard family is listed at 73 Shore A and 62 Shore A at those same gauges.
Miraclon lists finished Flexcel NXH plates at 71–77 Shore A for 0.045 inch and 63–69 Shore A for 0.067 inch, with lower ranges for thicker gauges.
These examples do not define an industry-wide chart. They show that plate family and plate thickness must stay attached to the hardness value. A Shore A number copied without its supplier, product, gauge, and test condition can describe the wrong plate.
How hardness changes print behavior
A harder plate surface resists deformation under impression. DuPont positions its DPI hard-durometer plate for sharp type, open reverses, low dot gain, and high-quality packaging work. That does not mean a harder plate automatically improves every job.
Softer plates can conform more readily to an uneven substrate. In an FTA article on corrugated printing, DuPont described a lower-durometer plate for B- and C-flute board where improved conformity helped solid ink coverage and impression latitude without requiring the same pressure as a conventional 33–34 Shore A corrugated plate.
The practical tradeoff is job-specific:
- harder plate constructions can support fine detail and resist impression-related deformation;
- softer constructions can improve contact and solid laydown on rough or uneven surfaces;
- the mounting tape changes the effective compressibility of the plate package;
- plate surface, screening, anilox, ink, substrate, and impression still shape the printed result.
Treat hardness as one controlled variable inside the print condition, not as a shortcut for selecting a plate.
Do not confuse plate hardness with plate thickness or relief
Plate thickness is the total gauge from the polyester backing to the printing surface. Relief depth is the height between that surface and the plate floor. Hardness is the plate’s resistance to indentation.
The three values interact, but they are not interchangeable. A supplier can offer different durometers at the same gauge. A processing change can alter the finished plate condition without changing the nominal raw gauge. A different tape hardness can change impression response even when the plate itself is unchanged.
For troubleshooting, identify which variable actually changed before blaming “the plate.”
What belongs on the job and plate record
A repeatable plate-hardness specification should keep:
- Plate identity: manufacturer, product family, material type, gauge, and lot.
- Hardness reference: supplier-rated Shore A range and a measured value when the shop’s QC plan requires one.
- Processing condition: exposure, processing, drying, finishing, and the finished relief and caliper.
- Mounted package: tape family, tape thickness and hardness, cylinder or sleeve, and mounting condition.
- Print condition: substrate, ink, anilox, screening, impression, speed, and approved sample.
If a rerun only recalls the artwork and plate gauge, the shop can substitute a different hardness or mounting package and get a different result. A flexo-native MIS keeps the approved plate construction and print evidence on the customer and job record so the next order starts from the verified condition.
The short version
Flexo plate hardness is usually reported in Shore A, but the number only makes sense with the plate family and gauge. Harder and softer constructions solve different print problems. Record the approved plate, tape, processing, substrate, and press condition together so a rerun repeats the full print system rather than one isolated specification.
Flexo plate hardness FAQ
What is flexo plate hardness?
Flexo plate hardness describes how strongly a finished photopolymer plate resists indentation. Suppliers usually report it on the Shore A scale. The value belongs to a specific plate family and gauge, not to flexo plates as one universal category.
What Shore A hardness should a flexo plate have?
There is no single correct Shore A value for every flexo job. Supplier data shows finished plates across a wide range, with the choice depending on plate family, gauge, substrate, image content, mounting system, and validated press condition.
Are harder flexo plates always better for fine print?
No. Harder plate families are often designed for fine detail and controlled dot gain, while softer plates can improve conformity and solid ink transfer on uneven substrates. Plate surface, tape, screening, ink, anilox, and impression also affect the result.
What plate-hardness data belongs on a flexo job ticket?
Record the plate manufacturer and family, gauge, supplier-rated durometer, measured result when QC requires it, material lot, processing condition, mounting tape, substrate, press condition, and approved print result.
Sources and related reading
- DuPont Cyrel DPI product data — hard-durometer plate positioning and Shore A values by gauge.
- DuPont Cyrel DFS product data — medium-hard plate data, ink transfer, and Shore A values by gauge.
- Miraclon Flexcel NXH technical specifications — finished-plate Shore A ranges across common gauges.
- FTA: Finding a solution for uniform ink issues on corrugated board — lower-durometer plate behavior on uneven corrugated substrates.
- Flexo printing defects — a plate-versus-press troubleshooting method.