Robert Welch Signature and Professional kitchen knives achieved an “Excellent” CATRA rating for both sharpness and edge retention when tested to the ISO 8442-5 standard.

This internationally recognised test measures how sharp a knife is when new and how well the blade maintains that sharpness over time.

Testing was carried out using specialist CATRA (Cutlery and Allied Trades Research Association) edge-testing machines, which provide an objective and repeatable way to measure knife cutting performance.

Based on 56 plain-edged Robert Welch knives tested on CATRA machines from the Signature and Professional ranges:

Average sharpness (ICP)
111.093 mm

Average Cutting Edge Retention (CER)
652.157 mm

This ‘Excellent’ rating places Robert Welch knives in the highest performance category, delivering consistently high cutting performance for longer.

The ISO 8442-5 test is designed to measure the cutting performance of kitchen knives under controlled laboratory conditions. During the test, the blade is drawn back and forth across a specially developed synthetic card containing 5% silica, which gradually wears the blade edge in a controlled and repeatable way.

The CATRA machine maintains consistent test conditions, including:

• Downward force: 50N
• Stroke length: 40mm
• Cutting speed: 50mm per second
• Number of strokes: 60 cuts for a straight-edged knife

These consistent conditions allow knives to be compared fairly using the same benchmark.

Sharpness is measured using Initial Cutting Performance (ICP). This measures how much of the test card is cut during the first strokes of the test.
The more material cut, the sharper the blade.

Edge retention is measured using Total Card Cut (TCC). This records the total amount of test card cut during the full test cycle.
The more card cut, the longer the knife maintains its cutting performance.

A knife that stays sharp makes every day cooking easier and safer.
When a blade loses its edge, it requires more force to cut and can slip more easily on ingredients. A knife with good edge retention continues to cut cleanly and precisely, improving control and reducing effort.

The ISO 8442-5 test measures how well a knife maintains its cutting performance over repeated use. Knives that achieve an “Excellent” rating maintain their sharpness significantly longer before needing maintenance.

Our knives are designed not only to perform exceptionally when new, but to maintain that performance for many years.

To keep your knives sharp, we recommend:

• Sharpen regularly
Use our Hand-held Sharpener to retain sharpness and keep the blade edges aligned.

• Replace the wheel
Replace the ceramic sharpening wheel periodically, or as needed, to keep knives performing at their best.

• Use a wood or nylon chopping board
Choose a wood or nylon chopping board to protect knife edges as the softer surface absorbs impact to protect knife edges and ensure long-lasting sharpness.

• Store safely
Keep your knives safely stored and sharper for longer by using one of our knife blocks, in-drawer units, or magnetic racks-each designed to protect the blade edge.

• Handwash for best results
All knives are dishwasher safe, but for optimal performance handwash with warm, soapy water, dry immediately, and use a microfibre cloth.

With simple care, your knives will continue to deliver the high level of performance demonstrated in the ISO testing.

Further details about the ISO 8442-5 knife performance standard can be found here: https://www.iso.org/standard/30037.html

Discover how our award-winning kitchen knives are forged from a single piece of stainless steel for precision and performance.