Waterproof batting?
 

A friend wants to learn to quilt-yay! She wants to make a table runner. BUT....she wants it to be waterproof. I have searched online for waterproof batting, and not had any luck. Would a flannel backed vinyl tablecloth work for the backing (with a layer of regular batting or insul bright)? Would it be difficult to machine quilt in the ditch? Any other ideas? Thank you!

Yes, use a flannel backed vinyl tablecloth for the backing. You can use any batting you like but I'd go with a thin one.

I would test to see if insulbright is waterproof but anything you sew thru, the DSM needle will make very tiny holes. I would just put a vinyl piece under the runner.

Why not just make a regular table topper and spray waterproof on it?

2 options I can think of:
1) Make the runner normally, quilt it, then add the vinyl and birth it or just bind. Don't quilt thru the vinyl. As mentioned before, the perforations from the quilting stitches will act like a sieve.
2) Do some research on PUL. It is available at JoAnns & some WMs. This is the stuff that you make diaper covers out of. Some brands will seal around stitches when washed and/or dried in hot water, some won't. I would buy a small amount and experiment.

I'm sure the tabletopper won't have liquid poured all over it so the stitching holes won't be a problem. The batting will absorb what little moisture there will be and the vinyl will keep it from the tabletop.

I use the backed vynal for this kind of project. I put the plastic side toward the topper so that the soft fabric backside is toward the table.

If using the flannel backed vinyl I wouldn't add batting. I like my table pieces to lay flat, if you add batting it will puff up & could create places where items fall over.

You could make the runner then us the iron on vinyl on the back?

I haven't used vinyl on a table topper, but I did make a changing table pad using a vinyl tablecloth. I did not do any quilting on it, just let the batting lay flat and be stitched in all the way around since it wouldn't have much reason to shift as the table pad was just wiped off with baby wipes. Don't know how long it was usable as we passed it on after my grandson was out of diapers.