Identifying fabric

You can try to stick masking tape to it.  If it has a silicone coating the tape won’t stick (hardly at all).  Or other tape.  But I think silicone coated fabric is niche, you probably don’t have any of it.

You have a box or something, but paper towel on that, fabric over that, wait for rain.  Weight down edges of fabric so it doesn’t blow away.  You could use a hose but it’s hard to simulate the properties of real rain.

For DWR coating test – towel, fabric, puddles of water on top.  Good DWR will prevent the water from going through.  Really good DWR will prevent the water from going through for 24 hours.

That’s what I’ve done before.

You could weigh fabric, calculate ounces per square yard (or g/m2 for the civilized world).  That’s a useful number.  If it’s heavy fabric you could use to make a prototype to use and evaluate your design, hone your skills.

Hey Jerry, thanks for the suggestions.

I’m not sure I followed your directions with the paper towel…I believe the rain wicked.  As for the tape test, it didn’t stick well to most but still had some grip.

I came up with a different test, I took my collection of Talenti jars (man I eat too much of that stuff) and some large rubber bands.  Then secured a sample of each fabric over the jars and pulled taut then set them out in a tub just in time for a storm to come through.

This isn’t true test as material was horizontal so water wouldn’t shed like it would when strung up and a couple jars tipped over due to buoyancy and failed ( I retested and later and they worked.  Afterwards I carefully removed the material and weighed the water (if any) to compare. Then wiped the jars with a paper towel to detect any moisture that may have not ran out.

As a second test, I grabbed a 50 ML syringe (from sawyer mini kit) banded a sample of fabric to the end and pushed for all my worth.  Obviously not a scientific HH test….but a couple of these I ballooned and stretched till I couldn’t push any harder and not a single droplet….2 of those also had Zero moisture in the jars…so I think I have a couple winners.

Now, I just need to precisely cut and weigh samples to calculate the g/sqyd.

I can already tell compared to commercial products that this is likely 1.9 silpoly…but free is well FREE.  And it’s something to do when stuck at home on a rainy day.

HH?  It sounds like you’re advanced : )

If water wicks through then it’s not waterproof and not even DWR

I have tested some DWR fabric that didn’t wick water through even after a day (M50 from thru-hiker) and DWR that wicked through within an hour or so (some unnamed fabric)

I’m sure I didn’t do the test right.   I’m assuming the intent was to put the paper towel in the box with the fabric over the box.  I laid the fabric over the paper towel ON the box.  Not a single one passed,  yet 3 of those I could not press water through with the syringe and half of them had little to no water after a storm dumped an inch of rain in an hour.

I’m going to build small tarp or rain kilt with and see how they do.  Worse comes to worse…I’ll get some sewing practice.

paper towel is just to indicate if water gets through

As a general rule if you can can’t blow thru it, it’s pretty water repellent and would likely hold up for use as a tarp where water is allowed to run off. If you can’t suck air thru it, even better.

Having spent rainy nights under uncoated parachute silk, you can get away with a lot if the pitch of the tarp is steep.

However, if you are going to make the effort to sew a complex project, you might want a known quantity to work with.

If your hose has high pressure (without one of those backflow guards at the hose bib) you could hold the fabric tight by hand around the hose opening and turn the water on full. If no beads of water make it thru (testing in several spots) you should be good to go.

Not sure if my bib has backflow, pretty sure it doesn’t. I’ll probably try that test as well.

I’ve decided to try some smaller projects (shorts or maybe jacket) to see how some of these hold up.