Well, whichever side of it happens to be facing up when I drop it into water.

plastics tend to be more hydrophobic. But also your observation that this behavior changes when "new" or "clean" is relevant. If so, it would be about whatever is coating the surface also. And the weight of the part of course. Can you zoom in on the holes?

Interesting proposition @PeteW ! Could you perhaps explain why it would matter that stainless steel is neutral / hydrophilic? Also: I intend to make the final product out of stainless steel - this plastic version is just a prototype. The layered solution is therefore not needed.

fantastic. Then no worries about final product. What you describe sounds just like the effect of surface tension. This is related to hydrophobic/hydrophilic. I tried to give a qualitative description here: engineering.stackexchange.com/questions/58463/…

Well, I don’t think that weight is the issue here. When I try to force the strainer down, the air bubble just remains where it was. Also, I could do more than just send a picture - I could share my 3D model 😉.

Hmm. The micro geometry - texture, roughness, sharp edges near holes - would also come out different in stainless steel. And this would change how much the air-liquid interface (or entire bubbles) can "grip" in practice. A formed and then polished or even electro-polished stainless part would be quite smooth

Hi Pete! 😉 Thank you for helping me out with this little project of mine.

No prob

You wanted a closeup of the holes, right?

Yep. Also, if you want to confirm it's really a surface tension effect you can try "using" your device with soapy water

I didn’t think of that! Sounds clever 😁. But could you guide me through the logic? What would doing so prove?

Especially since the final product is to be used with real water and stainless steel - not soap

That your device's functional issue would be resolved, if there were a way to make the air/liquid boundary break free from the holes

Which wouldn’t be present when stainless steel comes into contact with water?

I'm going by what I imagine is happening based on your description and the one photo. So might be worth the experiment

My phone’s camera doesn’t seem to take good macro photos…

The best I can do is send a 3D model unfortunately 😅

Can you just make a screenshot of a section view? (and add it to the original question)

(I'll be back in a bit)

Sure! Also, I just tested the prototype with dish soap as per your suggestion and it seemed to make the problem worse? 😄

I won't post these to the question overview because they would probably make it bloated 😅

Ok. So to clarify, where is the air getting stuck?

Well, wherever side is facing upward when I place it into water

*whatever

Thanks again for your help BTW