Textile pH Knowledge

Overview

The national mandatory standards GB 18401-2010 and GB 31701-2015 clearly state that textile products for apparel, decoration, and home use sold in China must undergo pH testing and meet the relevant safety requirements.

Now, let’s take a closer look at textile pH testing.

1. What Is pH?

pH is a measure of the acidity or alkalinity of a solution. It reflects hydrogen ion concentration, and the formula is pH = -lg[H+]. The value usually ranges from 1 to 14, and 7 is neutral. The lower the pH, the stronger the acidity. The higher the pH, the stronger the alkalinity.

2. Why pH Testing Matters

Human skin has a slightly acidic surface, usually around pH 5.5 to 6.0. This weakly acidic environment helps inhibit the growth of certain harmful bacteria and protects the skin from infection.

If a textile product is too acidic or too alkaline, it can disturb this balance. As a result, the skin may feel itchy, irritated, or even allergic.

3. How Textile pH Is Tested

To test textile pH, the fabric is first extracted with distilled water or deionized water. Then, a pH meter with a glass electrode measures the pH of the extract.

4. Why Textile pH May Exceed the Limit

Several factors can push pH out of range.

Dyes Used in Production

Common reactive dyes, vat dyes, and sulfur dyes work under alkaline conditions. Even if the fabric is washed properly, the pH of the process water can still affect the final result.

Printing and Finishing Processes

After scouring, dyeing, printing, and other finishing steps, textiles such as cotton, wool, silk, polyester, nylon, and acrylic may still retain alkali, acids, and auxiliaries. If too much chemical assistant remains, or if post-washing is not thorough enough, the fabric pH may exceed the standard limit and affect wear comfort.

Fabric Structure

Fabric thickness also matters. Thin fabrics are easier to wash, so their pH values are often lower after dyeing. Thick fabrics are harder to wash thoroughly, so their pH values may stay relatively higher.

Testing Errors

Lab operation can also influence the result. Differences in moisture content, extraction temperature, and extraction time can all affect the measured pH value.

5. How to Improve an Out-of-Range pH

If the fabric is too acidic, neutralize it with alkali. If it is too alkaline, neutralize it with acid. In general, acetic acid or citric acid works for acidic correction, while soda ash (sodium carbonate) works for alkaline correction.

You can also improve the dyeing and finishing process by increasing washing steps and strengthening post-treatment control.

In addition, choosing better raw materials and dyes from the start can help prevent pH problems at the source.

Conclusion

Textile pH is a key safety and comfort indicator. It affects both skin compatibility and product quality. Therefore, manufacturers should control pH carefully during production and make sure the final fabric meets the required standard before it reaches the market.