Things You'll Need
Moisturizing bath soap
Welding jackets are heavy leather jackets that are designed to protect workers' arms and bodies from flying sparks and debris while they are welding. These jackets are for serious work use, and as a result they generally are not kept in spotless condition. However, the dirtier the leather gets, the stiffer it becomes, and the smell can become unpleasant. Cleaning a welding jacket on a semi-regular basis will prolong the wearability and help you enjoy working while wearing it.
Moisten a rag. You can get it completely wet with lukewarm water, but then wring it out so that it is barely damp.
Place a few drops (no more than four) of moisturizing bath soap on the rag. Knead the rag so that the soap is worked through it.
Gently scrub the jacket. If it is heavily soiled, you may need to rinse and apply more soap to the rag periodically so that you do not just rub the dirt around. The soap will not only soften up the leather where it has gotten stiff, but it will also make it smell better.
Rinse off the soaped areas as you go. Use a separate, also barely damp rag to rinse off the soaped areas each time you complete scrubbing a spot. This will keep the soap from drying on the jacket. Do not use water directly on the jacket, but rather use the damp rag to rub the soap off the jacket. Rinse out the "rinse rag" periodically as well.
Condition the welding jacket. Use a leave-on leather conditioner to really make your welding jacket comfortable and supple again. You can work the conditioner in with a clean, dry rag and let it remain on the leather to keep it from cracking. This is very important since welding jackets will need to be cleaned more often than other leather jackets in most cases, and the conditioner will keep them pliable and easy to work in.
If your welding jacket is old and mildewed, spot treat the mold and mildew with rubbing alcohol before you start the cleaning process.