What Is a Lab Dip? The Short Answer
If you are a brand owner with a colour in mind, or a buyer with a bulk order about to start, a lab dip is the small dyed swatch a mill or factory makes to show how close it can get to your reference colour on your actual fabric. You review it, approve it or send comments, and the approved lab dip becomes the colour standard for the bulk dye lot. Without that step, the first time you see your colour may be on the finished goods, which is the most expensive moment to find out it is wrong.
The sections below show how a lab dip differs from other colour samples, how the approval runs from reference to bulk, why colour shifts between fabrics and lights, and what to do when the bulk does not match. This is practical guidance for buyers; it is not a laboratory standard, so ask your factory for its own procedure and tolerances.
Lab Dip vs Strike-Off vs Bulk Dye Lot
Three terms get mixed up, and mixing them up is how approvals go wrong. They describe three different things at three different stages, and each one answers a different question about colour.
Lab dip, strike-off and bulk dye lot compared
| Term | What it is | Question it answers |
|---|---|---|
| Lab dip | A small swatch dyed in the laboratory on your fabric to match a reference colour | Can the dye house reach this shade on this fabric? |
| Strike-off | A small printed sample of artwork on fabric, used for print colours | Do the print colours, placement and detail look right on the fabric? |
| Bulk dye lot | The batch of fabric or yarn dyed for production, usually in a large machine | Does the production fabric match the approved standard? |
| Pre-production sample | A finished garment made from bulk fabric before the order is cut in full | Do the garment, fabric and colour agree as a whole? |
Terminology varies slightly between mills and factories. Confirm what each term means in your supplier's process.
A lab dip is made in a small vessel under laboratory conditions, whereas the bulk lot is dyed in a much larger machine, so the two can differ even when the recipe is the same. That is why the lab dip approval is only the start, and why a bulk lot still needs its own check. Our guide to garment sample types shows where each sample sits in the sequence.
The Lab Dip Approval Workflow, Step by Step
A clear workflow keeps everyone looking at the same thing. The path below runs from your reference to the approved bulk lot, and it works for solid-dyed knits and wovens alike. Strike-offs follow a similar logic for printed fabrics.
From lab dip to bulk approval
- 1Supply a referenceProvide a physical colour standard, the target fabric and the light you want the colour judged in.
- 2Receive lab dip roundsThe dye house sends one or more swatches, often with several options per colour, labelled and dated.
- 3Judge under agreed lightCompare each swatch with the reference under the same light sources, then approve or comment in writing.
- 4Dye the bulk lotThe approved lab dip becomes the standard; the factory dyes bulk fabric to match it.
- 5Approve the bulk lotCompare bulk fabric with the approved lab dip, within the agreed tolerance, before cutting.
Each step has an owner, and the table below spells out who normally holds which approval item. Agreeing this before the first lab dip is requested removes most of the arguments later.
Colour approval items, purpose and signatory
| Approval item | Purpose | Who normally signs |
|---|---|---|
| Colour reference | Defines the target shade | Brand or buyer |
| Lab dip approval | Confirms the shade on the actual fabric | Buyer, with factory merchandiser noting the approved option |
| Strike-off approval | Confirms print colours and placement | Buyer |
| Tolerance statement | Sets how much variation is acceptable | Buyer and factory together |
| Bulk fabric approval | Confirms the dyed lot matches the standard | Buyer, or an agreed inspector |
| Pre-production sample | Confirms the finished garment | Buyer |
A typical division of roles. Your own contract and process may differ; write down who signs each item.
Why Colour Varies: Fabric, Dye Lots and Light
Colour does not travel unchanged from a reference to a finished garment. A shade that looks right on one fabric can look different on another, and the same swatch can seem to change when you move it from daylight to shop lighting. Understanding the causes makes it easier to choose which ones to control.
Illustrative split of the causes of colour mismatch
- Fabric substrate25%
- Dye lot variation25%
- Lighting and viewing conditions20%
- Finishing15%
- Reference quality15%
Illustrative only. The segments are an assumed teaching split to show that several causes act together; they are not measured data, and the real balance depends on the product.
Fabric and fibre
Different fibres take dye differently. Cotton, polyester and blends use different dye systems, and the construction and finish of the fabric change how light reflects from it. A colour matched on one fabric is therefore not automatically right on another, even if the shade name is the same. See our guide to fabric dyeing methods for the differences.
Dye lots
Each production batch is dyed separately, so small differences between lots are normal. For a single garment panel this rarely matters, but if the front and sleeve are cut from different lots, or a matching set is made from separate batches, the difference can show. Ask the factory how it controls shade within and between lots.
Light and viewing
Metamerism is the name for two colours that match under one light but not under another. A lab dip approved under warm office lighting may look different under daylight or retail lights. Agree one or two light sources for judging, and have both parties use them.
Colour Matching Clothing: References and Light Sources
Good colour matching starts with a good reference. A physical swatch that both sides hold is the most reliable standard, because it can be compared directly. A numbered colour from a standard colour-reference system is useful as a common language, but it is a guide on paper, and the dye house still has to match it on your fabric.
Screen colour or physical swatch as the reference
Physical swatch
- A physical swatch can be compared directly with the lab dip
- It is the same object for both parties
- It makes a written approval easy to verify
Screen or printed card
- A screen shows colour differently on every device
- Printed colour cards can fade or vary by batch
- A reference on a different fabric will not match the lab dip exactly
Use the screen only to communicate intent; use a physical standard for approval.
Whatever reference you use, record which light source you used to judge it. Good practice is to view both swatches side by side in standard daylight and in the light in which the garment will be worn, then note the result. The test methods used for colour assessment are published by standards bodies such as AATCC and ISO, and your factory can tell you which it follows.
Setting Colour Tolerances You Can Enforce
A tolerance is the amount of difference between the approved standard and the bulk that both sides agree to accept. Without one, every difference becomes an argument. With one, the question is simple: is the bulk inside the agreed limit or outside it?
Agree the method as well as the limit. Some factories judge visually under a light booth against a grading scale, and some use an instrument that reports a numerical colour difference. Neither is wrong, but the two should not be mixed in one dispute. Ask your factory which method it uses and what limit it applies, then put both in writing alongside the lab dip approval.
A sample colour-approval effort split
Illustrative effort
Illustrative only, assuming a solid-colour order where lab dips are done first and the bulk lot is checked before cutting. Not measured data.
What each approval step controls
1 dot = low, 5 dots = high
| Lab dip | Strike-off | Bulk approval | |
|---|---|---|---|
| Shade of dyed fabric | ●●●●● | ●●●●● | ●●●●● |
| Print colours and placement | ●●●●● | ●●●●● | ●●●●● |
| Match across dye lots | ●●●●● | ●●●●● | ●●●●● |
| Effect of finishing | ●●●●● | ●●●●● | ●●●●● |
| Match on the finished garment | ●●●●● | ●●●●● | ●●●●● |
Indicative ratings of what each stage can confirm, not test results. A bulk approval is the only step that covers the actual production fabric.
Our guide to shade variation in denim bulk orders shows how this works when the product is washed after dyeing, and denim colour fastness and crocking covers rub and wash performance.
What To Do When Bulk Does Not Match the Lab Dip
Even with good approvals, a bulk lot can come back outside the tolerance. Do not cut the fabric into garments before you check it, because once it is cut the options narrow quickly. Work through a short list instead.
- Compare the bulk fabric with the approved lab dip under the agreed lights, and photograph both side by side.
- Check the difference against the written tolerance and the method used to set it.
- Report the issue to the factory in writing before cutting, with the photographs.
- Ask for the factory's proposal: re-dye, accept with an adjustment, or use the lot for a different style.
- Record the decision and its cost impact in writing, and keep the approved lab dip as the standard.
The reasons bulk can differ from the sample go beyond colour, and our guide to bulk production vs sample covers the others, while the garment testing guide lists the tests to request.
A Colour Approval Checklist for Your Next Order
Use this checklist when you brief a factory on colour, and again before you approve the bulk lot. It condenses the whole workflow into questions you can answer yes or no.
Colour approval checklist
- Do both sides hold the same physical colour reference?
- Is the lab dip made on the actual bulk fabric or yarn?
- Have you agreed the light sources for judging?
- Is each lab dip labelled and dated, with the approved option recorded in writing?
- Are the tolerance and the method of measuring it written down?
- Will the bulk fabric be checked against the approved lab dip before cutting?
- Have matching items, such as a set, been planned to come from the same lot?
- Is the person who signs each approval named?
A planning aid. Ask your factory for its own procedure and adjust the list to your product.
Keep the physical approved lab dip, date it, sign it, and have the factory keep its own copy. If a dispute starts, you are comparing the bulk with something both sides can hold in their hands. For fitted shapes, apply the same discipline to your fit comments.
One question before you place your next order: if the bulk fabric arrived tomorrow, what exactly would you compare it with, and who has signed it?
How Ruhrose Approaches Lab Dip and Colour Approval
Ruhrose develops hoodies, jersey, denim and woven casualwear for UK buyers, with production in Bangladesh, and colour approval is part of sampling. We ask for a physical reference, agree the light and tolerance in writing and, where the product allows, check the bulk fabric before cutting. We cannot promise that two dye lots will look identical, and denim in particular has natural shade movement, so we aim to agree limits and flag differences early. Drapey woven categories such as dresses have their own colour behaviour, covered in our dress manufacturer guide. For more on how we work, see Ruhrose's clothing manufacturing services.