So you've got a fancy new gi and you want to do everything you can to keep it looking good and fitting right for a long time. Here's your guide to washing, drying, and shrinking (or not shrinking) your gis.
Do I need to do a vinegar soak before washing a new gi for first time?
No. This is not necessary for new gis. This practice comes from the idea that you need to "set" the dye so it does not run in the wash. Some gi companies may have problems with extra dye on their fabric so they can get a supersaturated color, and that first soak and wash helps remove dye that would run off, but the vinegar doesn't do anything. If you want to be safe about colors running, you can wash a new gi by itself, no vinegar needed.
Can a vinegar soak get funky smells out of a gi?
Yes, that is a fine use of vinegar. Soaking gis (or any stinky gym clothes) in a mild vinegar solution is a common home remedy for getting bad scents out. You can also buy special detergents formulated specifically for removing strong odors.
To avoid the funk in the first place, wash your gi as soon as you can after training and don't let it sit in the washer afterwards too long. Don't cram your sweaty gi in a gym bag and forget about it, and don't throw it in a laundry hamper for a few days to ferment (and ruin the clothes its sitting on).
Should I machine dry my gi?
That depends on if you want to shrink the gi (see below) and if you are worried about extra wear and tear. Tumbling around in the dryer will wear out fabric faster, but it will also make it feel softer.
How do I shrink a gi?
This is a good use of a dryer. After washing a gi, throw it in your dyer, and the hot air will shrink the cotton. Start conservatively, not going too hot yet. After shrinking, the cotton will stretch again (think of how tight freshly washed and dried jeans are before they relax). It may take a few tries before it gets to your desired size/length. Once you're happy with it, you probably want to switch to air drying to keep the fit you like. Sweat, body heat, and being yanked on in training will stretch it again too, so expect some changes over time.
Can I bleach my gi?
The common advice is to not bleach a white gi because it will weaken the fabric. I have tried to find the scientific explanation for this, and per the chemists, a little bleach should not destroy cotton, so you are probably safe occasionally adding a small amount of bleach to the wash if you want to keep the whites at their whitest. That said, not everything on a gi is white, so expect lightening of colored stitching, drawstrings, belt loops, patches, etc. They make color-safe bleach for this purpose.
Should I wash with cold or hot water?
You are fine washing with cold water. Modern detergents work in cold water, and you save on energy.
How do I get a stain out of my gi?
I'm going to assume we're talking about blood stains here, since it seems like if I wear a new white gi, that's the day I get paired with someone who has all their knuckles bleed everywhere they grip. I recommend spot treating it with a stain remover and washing it as soon as you can, before the stains have a chance to set.
Following this advice should give your gi a long and happy life!