Q. Is there a way to whiten white acetate fabric that has turned dingy/yellow?
A. I’m a little confused by your title as acetate usually is a little more “frail” than rayon. Have you tried just a normal wash (with the acetate garments by themselves)? Acetate can occasionally pick up stray dyes. Maybe a good warm wash with detergent and a more mild oxygen bleach like our Clorox2® Stain Remover and Color Booster would help. Still some lingering yellowing? Try a 1-hour presoak with Clorox2® Stain Remover and Color Booster and follow label instructions.
If you want to try something a little stronger, it would be Clorox® Regular Bleach2. For this, I would recommend you do the quick Bleachability Test (2 tspn Clorox® Regular Bleach2 in 1/4 cup water; apply a drop on a hidden colored area like inside seam, hemline or cuff; wait 1 minute and then blot with towel); no color change means it is safe to use bleach on the item. Any color change could also show you the amount of change in color that likely will occur if you proceed with the liquid bleach usage. Want to proceed? Try a presoak (1/4 cup Clorox bleach per gallon of cool water for 5-10 minutes), then wash in warm water using detergent and 3/4 cup Clorox® Regular Bleach2. It may take a couple of treatments to achieve your desired result.
After either treatment, I would consider air drying to maintain the garment’s shape and minimize shrinkage potential.