I used a paper mask over my nose as I’m sensitive to the smell
Do it outdoors, in an open space, with plenty of ventilation.
Diluted: 1 cup of beach for 4 cups of warm water.
Wearing gloves and a wooden spoon, submerge the denim into the solution. Once it started to light it up, remove it. I left for 5 minutes.
Be careful and keep watching the item as bleach can damage it. Remove carefully and wash very well ( wearing gloves and a wooden spoon) avoid touching it for a while. Some people use a bleach stopper as hydrogen peroxide… I didn’t.
Spend some time washing under running water, then soak in the bath tub for an hour with warm clean water.
Wash in the washing machine by itself in warm cycle.
Since then I have washed again and no running of beach on other clothes.
How to refashion the dress:
Using a rotary cutter, cut a straight line after the last button. From the bottom part, remove 2 cm.
Pin it back to the dress, with the front part at the back and the back on the centre front. Start by the side seams and pin around. Sew a seam allowance of 5/8 (1.5 cm). Overlock the excess. That creates a nice back vent.
Create fisheye darts on the bodice. Measure the centre of the bodice and pin the start of the dart from under the pocket to the waist, diminishing until the dart fades. Press!
Just show that having a good fit really makes a different on an garment. Have you been refashioning later?