From Subjective Hand Feel to Objective Data: The Core Principle of qmax Cool-Touch Testing

What is qmax?

qmax is the maximum heat flux, usually expressed in W/cm². When skin comes into contact with a fabric or material, heat rapidly transfers from the skin to the material. This instantaneous peak heat flow is called qmax.

The higher the qmax value, the cooler the material feels at the moment of contact.

qmax was proposed by Professor Kawabata of Kyoto University in the 1970s and is measured using KATO TECH’s KES-F7 Thermo Labo. It is one of the earliest systems developed to quantify the sensation of cool touch.

Why is qmax important?

In the past, cool touch, comfort, and hand feel were often evaluated subjectively by human judgment, which could easily lead to inconsistent results.

The value of qmax is that it allows users to:

• Objectively evaluate the cool-touch performance of materials

• Compare cool-touch differences among different products

• Establish clear product development targets

• Conduct competitor benchmarking

• Support the development of cool-touch textiles, sportswear, underwear, cooling mats, and other related products

  

qmax values measured under different test conditions cannot be directly compared

This is especially true for the ΔT temperature difference condition. ΔT refers to the temperature difference between the sample surface and the heat plate. The larger the temperature difference, the greater the heat flow, and therefore the higher the qmax value.

Sample	Surface qmax	Test Condition
Underwear A	1.70	ΔT = 10°C
Underwear B	2.00	ΔT = 20°C

At first glance, Underwear B appears to feel cooler. However, because B was measured under a higher ΔT condition, the two values cannot be directly compared. If converted to the same ΔT = 10°C condition, the qmax value of B would become 1.00, meaning Underwear A would actually have the stronger cool-touch performance.

Different standards use different ΔT conditions

Standard	ΔT Condition	Cool-touch Criteria
JIS L 1927	ΔT = 10°C	qmax ≥ 0.100 W/cm²
GB/T 35263-2017	ΔT = 15°C	qmax ≥ 0.15 J/(cm²·s)
CNS 15687 L3272	ΔT = 10°C	Criteria not specified in the document
FTTS-FA-019	ΔT = 10°C	qmax ≥ 0.140 W/cm²

qmax is not the whole picture of cool-touch performance

qmax only represents the instantaneous cool sensation at the moment of contact. It does not represent the complete wearing comfort of a material.

It cannot fully reflect:

• Sustained cool feeling

• Moisture absorption and quick-drying performance

• Breathability

• Non-sticky feeling against the skin

• Overall tactile comfort

Therefore, when evaluating cool-touch fabrics, qmax should not be the only factor considered. Other performance properties should also be assessed together.

Application industries

Industry	Applications
Cool-touch materials	Cooling mats, cool-touch underwear, sportswear
Automotive interiors	Instrument panels, leather, synthetic leather, seats, steering wheels
Cosmetics and hair care	Hair dryness sensation, cool sensation of cosmetics
Hygiene materials	Cool-touch masks, cooling sensation of sanitary products
Others	Fresh feeling after washing, crisp and refreshing sensation

Main KATO TECH cool-touch testing instruments

Item	KES-F7 Thermo Labo	KES-QM Warm/Cool Feeling Measurement Tester	FR07 Thermo Labo Compact Model
Equipment positioning	Standard thermal property testing system	Automated instrument focused on warm/cool feeling and qmax testing	Compact and portable thermal property testing system
Main functions	qmax, thermal conductivity, and heat retention testing	qmax warm/cool feeling testing	Thermal sensation testing for special shapes, curved surfaces, and irregular surfaces
Applicable standards	Can correspond to JIS L 1927, GB/T 35263-2017, and CNS 15687	Mainly emphasizes automation and high precision; standards are not specifically listed in the document	Mainly emphasizes flexible measurement; standards are not specifically listed in the document
Advantages	Compatible with major standards and highly expandable	Can perform up to 10 consecutive automatic qmax measurements, improving measurement precision	Portable, non-destructive, and suitable for special samples
Suitable samples / applications	Textiles, cool-touch fabrics, and standardized testing requirements	Samples requiring high precision, repeated testing, quality control, or R&D comparison	Hair, skin, round objects, mesh materials, uneven surfaces, and high-temperature/high-humidity environments
Operation features	Comprehensive functions; standard laboratory-type instrument	Built-in Thermo Cool unit, compact design, and touchscreen operation	Lightweight and portable; small sensor enables point measurement