Can UV Light Detect Laundry Detergent?

I bought a new swimwear on eBay and suspect the item has been washed. Can a 365nm UV flashlight detect laundry detergent in the fabric and if so, what signs should I look for? I have a Convoy S2+ and a ZWB2 filter bought from Simon on Aliexpress coming in the mail.

Tapis said:

I bought a new swimwear on eBay and suspect the item has been washed. Can a 365nm UV flashlight detect laundry detergent in the fabric and if so, what signs should I look for? I have a Convoy S2+ and a ZWB2 filter bought from Simon on Aliexpress coming in the mail.

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Laundry detergent certainly fluoresces under UV light. However, if it was rinsed, there wouldn't be much detergent left to see. Plus, the fabrics may be fluorescent anyway (like cotton is).

Smell it? Yeah, gross, but perhaps there's some perfume scent that would tell you.

Brighteners in detergent will show up. However, if the detergent is clean rinsing without brighteners it show not show up at all.

Many, but certainly not all detergents contain optical brightners to make clothes appear cleaner, and in general those optical brightners do fluoresce as blue under UV light. In order to useful however, they have to be able to survive rinsing, so in some respects they are much more like dyes than detergents. Unfortunately all their presence indicates is that at some point either the garment, or the thread or material that went into it were washed in a Detergent with optical brightners. In other words it has been washed, but there is no way of telling whether when in it was washed. It could be anytime from the time the threads that are used to make the material were produced, to after initial sale, and before return. So unfortunately the presence of optical brightners that fluoresce tells you very little other than the fact that it has been washed.

I was trying to build a case and get a partial refund. But indeed, the fabric could have been washed with some kind of chemicals prior to the making. The seller seems honest and reliable, so I won't insist. Thanks a lot for your feedbacks.

u would be suprised how much stuff u can see that u wish u didnt want too perhaps.. the light is pure uv so anything that naked eye dont see with the light u will see lol....