All denim is either sanforized (pre-shrunk) or unsanforized (in its raw cotton state). Soaking either type, if you choose to do it, has its benefits and can be an important step to undertake when starting a new pair of jeans.
How to soak your raw denim
The main reason to soak sanforized denim before wearing it is to remove some of the wax and starch in the finish of the denim. To soak your raw denim:
- Fill a tub with water (cold water for sanforized, hot for unsanforized)
- Turn your jeans inside out and fully submerge your jeans in the water. If parts of your denim float to the surface, put some weight over it.
- Let your denim soak for one to two hours. The water might look kind of murky afterwards but don’t worry, your denim is fine.
- Take your denim out of the tub and squeeze the excess water out
- Air-dry your denim. The denim will still be rigid, but will break in quicker now that the starch has been removed.
Another rationale for soaking sanforized denim is to “set” the indigo dye to reduce crocking. This is accomplished by filling a tub with cold water, one cup of white vinegar, one cup of sea salt and soaking the sunken jeans for one hour. Rinse in cold water and air dry.
The principal reason to soak unsanforized denim is to shrink-to-fit the fabric. Since the cotton is in its raw state, jeans made from unsanforized denim can shrink 1-2 waist sizes and 2-3 inches in length. The process is the same as above except for unsanforized denim, hot water is preferable (40°C/140°F).
In both cases, it is very important to keep the jeans out of the dryer and to air dry only.
Here's a handy infographic you can keep for yourself the next time you want to soak your own raw denim: