Lot-to-lot Variation

Definition and Overview

A lot is a production unit in which everything from raw material preparation to manufacturing, dyeing, and finishing is managed together under fixed conditions. Lot-to-lot variation can occur not only in textile, but also in thread, accessories, printed products, and more.

Even for the same product number, the condition of the raw material, the formulation of dyes and chemicals, temperature and humidity, and the settings of processing machines are not always exactly the same each time. As a result, differences may be seen between samples or textile delivered earlier and later lots.

How It Appears and Main Causes

What is especially checked as lot-to-lot variation is hue, shade, luster, and hand. In addition, differences may appear in textile width, industry weight, thickness, stretch, fuzzy texture, and the appearance of patterns.

In yarn dyed fabrics, differences in the dyeing result of the yarn affect the appearance of the woven fabric, while in piece dyed fabrics, differences in dyeing and finishing conditions affect the overall color and hand of the textile. The way differences appear also varies depending on the blend ratio of materials, structure, and processing details.

• Color difference means a state in which brightness, vividness, or color tone differs from the previous lot.
• Batch difference may refer to color differences caused by differences in production units such as dyeing vats or tanks.
• Because the appearance of color may change depending on the light source, the lighting conditions for inspection are also important.

Production Control and Impact on Main Applications

As a rule, the textile used for one garment or products displayed together in the same sales area should be planned from the same lot. If lots are mixed in the body, collar, pocket, belt, and similar parts, differences in color and texture may become noticeable.

For additional production, cutting for repairs, or special-order colors, it may not be possible to secure the same lot as the original run. It is important to allow for cutting loss and future additional quantities when planning the required amount, and to share the production plan at the time of ordering.

Selection and Handling Precautions

Before ordering, inspect the actual sample and the mass-production textile under the same conditions, and agree on acceptable ranges for color, hand, width, and other factors among the relevant parties. For color-sensitive matched-color products, also check combinations with contrast fabrics and accessories.

When the roll arrives, check the lot on the roll label or management slip, and sort by lot before cutting. If multiple lots must be used, cut with appearance in mind, such as separating lots by product unit or avoiding mixing them within the same product.

Color fading, shrinkage, and changes in hand caused by washing or cleaning are quality items separate from lot-to-lot variation. However, differences in appearance after washing may seem large because of differences in finishing conditions, so performing a preliminary test is reassuring.

Differences from Similar Terms

Color difference refers specifically to differences in color tone, brightness, and vividness. Lot-to-lot variation is a broader concept that includes color difference as well as differences in width, industry weight, hand, physical properties, and more.

Colorfastness indicates how resistant color is to changes or transfer caused by friction, washing, perspiration, light, and similar factors. Lot-to-lot variation, on the other hand, refers to differences in appearance and specifications between products from different production units, and the evaluation target is different from colorfastness.

Frequently Asked Questions

Can lot-to-lot variation be completely eliminated?

Differences can be reduced by controlling production conditions, but it is difficult to eliminate them completely because raw materials and dyeing and finishing conditions fluctuate. Using the same lot for the same product and securing the required quantity together is the basic practical approach.

Will an additional order have the same color as the first order?

Even with the same product number and color number, if an additional order comes from a different lot, the color and hand may differ from the first order. If additional production is possible, consider the future quantity at the time of the initial order and keep a sample for color matching.

Can textile from multiple lots be used in the same product?

Because differences in color and hand may stand out, mixed use within the same product should be judged carefully. If unavoidable, prioritize methods such as separating lots by product unit, rather than using them only in less noticeable areas, and check the appearance of the finished product.