craftgrrl | Screenprinting fine lines

I recently bought some finely weaved polyester silk in order to screen thin-lined artwork and am having an annoying issue with the very small thin lines. If this question is better suited in another forum, please let me know!

After burning the entire image, the thicker lines wash out easily, but the very small thin lines take a lot of water pressure and some fingernail scraping to wash out. Is this an issue with not burning long enough? Because eventually they wash away with some effort, just not very easily. As a result, when I attempt to screen, the thin lines do not appear or show up choppy. When I burn the screen, I'm using a transparency with glass on top.

Thanks in advance for any suggestions.