I've always had issues with white floss coverage. Improved by switching to Anchor's white, but many times, three strands were required. Recently I saw new-to-me types of floss on the Tube purporting to have great coverage and decided to try them. Doing a little research, I found a great explanation on Mary Corbet's site.
https://www.needlenthread.com/2014/02/cotton-floche-vs-coton-a-broder-up-close.html
These threads are non-divisible, single strand, and softer. Just like the coverage my chair cushion gets when I park myself, the thread's softness also spreads out and fills the space. One is called floche, the other is coton a broder (cutwork thread) available in several thicknesses. #16 is the heavier, #25 is most similar to the floche. I searched for days, only to find it unavailable in blanc except with a ridiculous shipping charge of $7.90 for a skein of floss. Finally, found them all on Needle in a Haystack. Their shop is more brick and mortar than online but you can click on the products in the left hand column for a searchable option.
If interested, here is the thread listing, just scroll down and click the DMC threads you are interested in, they have both the floche and coton a broder. The floche is a huge hank but you can order a smaller amount.
http://www.needlestack.com/WebStore/thread.html
Taking Carole for more tests today. I may drop her off at the door and have her ask an aide to get a chair and wheel her. Sometimes a sharp pain will grab and stop me in my tracks, which may cause me to release the chair's handle, which in turn activates the brake, and sends Carole flying.
Have a great day!!
**********************