Why do lighter colours fail the fastness test?

American Standard AATCC 150 and AATCC 172, two tests, often fail on light colour fastness.

So, is this problem caused by the dyeing factory? Or is it caused by the testing company or the customer?

This article aims to explain the problem’s causes and analysis. It seeks to identify who is responsible and to avoid unnecessary trouble.

1.The problem of the introduction

For example, customers often complain about notary public test reports. They failed AATCC150 or AATCC172 colour fastness tests. In the past, this kind of complaint is rare, because this kind of test is not often done. The rise of washing machines and laundry detergents has changed them. They evolved from a single soap or surfactant. Now, they are multi-functional detergents.

Dyeing factories must bear any problems. Tests are foolproof. Fabric buyers or middlemen handle all complaints.

Of course, the notary public test is not wrong, then you say the customer is wrong? He has an authoritative test report, you say the dyeing factory is wrong? He is puzzled, I put the fastness of the best reduction dyestuff are used or not, this problem in the end where? How to solve the problem? This is really a tricky problem.

2.The comparison of several methods of testing

AATCC150 is using AATCC 1993 fluorescent detergent, then the normal wash. We treat AATCC172 with 1993 WOB detergent and CLOROX 2. The first detergent is non-fluorescent. The second is fluorescent and contains a bleach. The principle is that chemical bleaching makes fibres whiter by destroying pigments. However, it can only improve their whiteness so much. Only use a tiny amount of bleach because it can damage the fibers. The fluorescent whitening agent absorbs invisible UV light. It then emits visible blue-violet light. This blue-violet light and yellow light can complement white light. So, fabric treated with the agent looks pure white and bright. Fluorescent whitening creates an optical effect. It does no harm to the fibre. It can make the fabric very white, but only a little.

Both standards contain a fluorescent agent. It did not cause a problem. We need to do some tests to see if we can clarify the problem.

The test fabric is 20*16/128*60 cotton twill fabric

Numbering	Colour	Bleaching	Milky white	Apricot	Khaki	Grey green	Coffee	Navy blue	Black
1	Colour change	3	4	4	4	4	4	4	4
2	Colour change	3-4	3-4	3-4	3-4	4	4	4	4
3	Colour change	4	2-3	3	3-4	4	4	4	4
4	Colour change	4	4	4	4	4	4	4	4
Dye		Fluorescent	Coating	Reduced	Original	Reduced	Active	Active	Active
Shade		Light	Light	Shallow	Shallow	Medium depth	Deep	Deep	Deep

Note: The detergent used for test method No. 1 for AATCC150 is AATCC 1993 WOB. Users analyze the test results using the detergent AATCC 1993 WOB. It is a workaround for the AATCC 1993 detergent.))

No. 2 represents the detergent chosen for the test method AATCC150 is AATCC 1993. (The test agent itself)

No. 3 is the detergent for AATCC test method 172. It’s AATCC 1993 WOB+CLOROX 2 (own test agent).

The detergent selected for test method No. 4 for AATCC172 is AATCC 1993 WOB + a non-fluorescent oxidizing agent, like CLOROX 2. (Workaround Method).

In the non-chlorine bleaching test, CLOROX 2 has bleach and a fluorescent whitener. It is hard to tell which is more effective. To distinguish this, we adopted test method No. 4. If you remove the fluorescent whitener from CLOROX 2, the color still changes a lot. This means the bleach is the main agent. Otherwise, the colour change is due to the fluorescent whitener. Otherwise, the colour change is mainly caused by the fluorescent whitener. The non-chlorine bleach contains mild sodium perborate as an oxidative bleach. Its hydrogen peroxide releases ecological oxygen to bleach.

We considered several situations in these four tests. Test 1 is non-fluorescent and has no bleach. And test 2 is fluorescent and has no bleach. Test 3 is bleach and fluorescent. Test 4 is bleach and non-fluorescent.

3. Analysis of the problem

We analyze the results presented above:

The colour change is due to the small fluorescent whitening agent after washing. Bleached number 1 and number 2 have a high affinity for it. The reason for the small colour change in number 3 is twofold. It has some fluorescent light in it. After washing, we lost some of that light. But, we added a highly-affine fluorescent light to replace it. So, the colour change is very slight. No. 4. There is no fluorescent agent. But, the new eco-oxygen’s sodium perborate decomposed and bleached the original backing fabric. It destroyed the pigment, so the fluorescence fell off. This chemical bleaching made up for it. Thus, the natural color change is small.

The milky white is different. After the number 1 wash, the colour change is small. But after the number 2 wash, the colour change is big. The added fluorescence makes its yellow light disappear. It looks fresher and whiter, which changes its colour. It is a colorant that can change and brighten the color. Under UV light, it has more sparkling fluorescence than the previous one. After No.3 washing, the change is greater. A two-pronged approach, chemical bleaching and optical whitening, is white on white. No. 4 colour change is not big because it does not have a fluorescent agent, only a trace of bleach, the role is not very big.

For apricot and khaki the reasoning is the same as cream. And from the grey-green, the change seems slight. It’s mainly due to the deep color. The base color has a significant percentage of trace dyes. This affects the color a lot. The trace colorants are too low to show a change compared to the large number of dyes. A fluorescent whitening agent will change the colour by X. The base colour has a dye depth of Y. If X/Y is greater, the colour change is greater. If the ratio is smaller, the change is less. This excludes colours that contain the whitening agent. The table shows that, the lighter the colour, the greater the change. The deeper the colour, the smaller the change. The test also proved that the dye choice had little effect on the premise’s depth.

4. Discussion

We can draw a conclusion based on the above test results:

Using AATCC150 and AATCC172 to test light colours will cause a large colour change (except for bleaching). But, as the colour gets deeper, the change will decrease.

Now we know that a fluorescent agent will change the colour. It is important to want to use it, which an intentional change of colour. So, we should not blame the dyeing factory’s color fastness for this change. There is a point where you can use a non-fluorescent detergent that will not change the colour. We consider this an unintentional change of colour. So, it should not change the colour or only change it a little. If it makes a big change, then it is the dye house’s problem.

So how can you define whether you are changing colours intentionally or unintentionally? If you pick a test method with fluorescent detergents, you are changing the color on purpose. And if you choose a method with non-fluorescent detergents, you are changing it unintentionally. If the colour change is outside the requirements, the dyeing factory is liable. If you change the colour on purpose, the dyeing factory is not responsible for any colour change. It must be reasonable.

Customers only care about the result. A failed test report from the notary public is the dyeing factory’s fault. They ignore any intentional color change. This causes grievances among dyeing factories. Many still don’t know what their problems are.

Of course, we can trust the notary public as a third party. If the test report’s notary public can, please add a line. It should note whether the change in colour was intentional or not. This would help to distinguish responsibility, as the notary can tell the difference. In the case of a large colour change, please follow up. Do an AATCC61-2A test to confirm if the change was due to unstable dyeing or fluorescent agents. If the result still fails, the dyeing factory is responsible. If it meets the requirement, the colour change is due to the fluorescent agent. Then this kind of trouble and dispute is much less, and will not be unreasonably entangled.

If there is no notary public line test, and do not know which type of detergent when the user complains about this problem, then it can be completely through the ultraviolet blocker to identify whether the colour change is intentional or unintentional. Before and after washing the two pieces of cloth side by side, we treated the top cloth with a UV blocker. If the color rating does not meet the requirements now, we deem it unqualified. This means it has poor colour fastness. If the colour rating meets the requirement, it qualifies. There is no issue with colour fastness.

Sometimes, the user is helpless. He lacks the expertise to choose a detergent. Even if he did, most laundry detergents contain fluorescent agents. So, manufacturers must produce some non-fluorescent detergents. They should mark these with a conspicuous word to give users more choices. Some may want the color unchanged. They should have the choice. The dyeing factory shouldn’t bear any unwanted responsibility.

If the dyeing factory ensures colour fastness, it should explain. Also, if the notary public notes it, that would help. If customers know more, clothing factories should add warning labels. Daily necessities containing chemicals should not use fluorescent detergents and must be marked. This gives end-users options. It will reduce complaints and improve harmony between us. Everyone will become more harmonious with each other.

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