Unveiling the Insights About Dishwasher Testing for Water Bottle Exports? Part 3

Every cup has a story, and life has its warmth. Hello everyone, and welcome to "Dong Dong's Cup Talk" I’ve previously shared information about dishwasher testing for water bottles. https://www.umbottle.com/ProductsDetail-VB-10523.htmlHowever, as time has passed, advancements in manufacturing processes and updates in testing requirements have made some of the earlier content outdated.

Recently, a friend reached out to me with questions about this topic, so I’ve invited Engineer Li, who has years of expertise in spraying and printing technologies at our factory, to share his insights. The following content is based on Engineer Li’s explanations, compiled and organized by me. https://www.umbottle.com/ProductsDetail-VB-10523.htmlDue to the depth of the topic, I’ll break it down into several standalone articles. Also, given the volume of information, there might be occasional data inaccuracies in my compilation. If you spot any, please feel free to message me privately, and I’ll make corrections as soon as possible.

### 3. Powder Coating vs. Paint Spraying: The "Face" of Qualified vs. Defective Products

Let me illustrate with two real-world cases.

Case 1: Qualified Powder-Coated Product

Last year, we produced stainless steel cups for an American outdoor brand, using high-quality epoxy-polyester hybrid powder. https://www.umbottle.com/ProductsDetail-VB-10523.htmlAfter 20 dishwasher test cycles, the surface retained its matte black color with uniform gloss, felt smooth to the touch, and showed no scratches even when scraped with a fingernail. This is a qualified product—like wearing a layer of armor.

What does a defective powder-coated product look like?

The year before, one batch used lower-quality powder to cut costs. By the 15th wash cycle, small white flakes, resembling dandruff, appeared along the rim of the cup base—a sign of coating powdering. https://www.umbottle.com/ProductsDetail-VB-10523.htmlIn more severe cases, the cup body developed fine "crazing" patterns, like parched earth, which eventually led to flaking, exposing the underlying stainless steel.

Case 2: Qualified Painted Product

For a Japanese client’s mug, we used a two-component epoxy primer with a polyurethane topcoat system. https://www.umbottle.com/ProductsDetail-VB-10523.htmlAfter testing, the gloss level dropped slightly from around 95 GU to 90 GU, which is normal and acceptable. The color remained unchanged, and the overall finish stayed intact.

What does a defective painted product look like?

The most typical issue is "blistering." Similar to skin blisters from burns, moisture penetrates beneath the paint film, forming small bubbles that burst when scratched. https://www.umbottle.com/ProductsDetail-VB-10523.htmlAnother issue is "peeling," where the entire paint film detaches like a layer of skin, indicating poor adhesion between the primer and the base material.