What's the thing that's left on the filter paper?

Which is the one that passes through the filter paper?

Newborn screening around the world is still done using similar filter paper.

Small particles like this do not settle out and will pass right through filter paper.

But when the filter paper was removed it turned back to its original color.

The patient then wipes the blood every 30 seconds with a filter paper.

To carry out the test, the urine is passed through the same filter paper several times.

The solution is placed on the soil sample held in filter paper.

Me wiped his eyes with a round disk of filter paper.

A test experiment might be using different grades of filter paper rather than string.