In short it depends what exactly you're bleaching and why. IE the material it's made of, some are unsuitable for standard household bleach but oxygen bleach can be used, some just not, and if you're talking yellowing stripes, general greying,ageing, minor mold spots, out break of mold spots, serious mold all over etc.
'Sheets that block summer heat waves' sound like they could be specialist plasticized material? Or something like shower curtains. Or equally, cotton, canvas etc.
TBH I do it all by eye, the state of a thing and what color the water goes, and when it darkens, to make decisions, on bleach/water ratios, and soaking times.
You may have old bottles of thin bleach around, in which case procedure differs, but generally nowadays it's thick bleach available only.
This is for white/cream cotton/canvas, and thick bleach only:
If you know the material is basically bleach safe and its naturally a light color, then basics are 1st) Do it when no kids around! A big plastic bucket in the bath, big wooden spoon or similar stiring stick. Rubber gloves or suffer the consequences to hands and nails, and cuts.
Wear old clothes in case of splashes, and remove things like bathmats or towels from vicinity.
I'm making an assumption there may be some mold spots in which case:
In the bucket; 1/2 litre of bleach to 1,5 litres of v.hot water stirred, then push any parts with mold spots into mixture, pummel/stir with spoon thoroughly, pull material out (watch your eyes) and dump in bath.
Immediately add another litre of v.hot water to bucket and put material back in, pummel a bit, leave for a couple of hours. If the water has gone properly grey or worse, then chuck and repeat, but stage two add a little more bleach and leave for several hours.
If the 1st step was just slightly greyed water, then add 2 to 3 litres very hot water and a little Ariel or similar, leave for a few hours and wash.
Wash out bleach thoroughly - it both eats and stains material if left in. If possible hang to dry in sunshine, but that's often impossible.
The longer you leave material in a bleach solution the shorter it's eventual lifespan, so if this is something you are likely to do annually - learn how long to leave soaking, before no further benefit, and remove then.
On the other hand somewhere on our threads from a couple of years ago, are aunts terrifying elderly mold affected (especially the linings) curtains, that she didn't want to replace. I soaked those overnight in a stronger solution approx 50/50 bleach and water, several times before I got clean enough water to soak in Ariel and just wash them, and they turned out amazingly well, and are still going strong enough - so it's all relative.
Shower curtains roughly 1/8th of a litre of bleach to 5 of very hot water for half a day and some squeezing/ pummeling.
HTH, shout if it doesn't make sense or it's another material.