A great costume needs to have “lived” so that it can sell the character you are portraying. The same way you would apply weathering to an armour, your soft parts needs attention too.
Step 01: WASH // wash the parts a couple of times to get the new fabric shine out. Wash with clear water only ( no other products needed), dry, wash, dry- repeat.
Step 02: AGE // Fabric naturally loose elasticity, get thinner over time/wash, holes may appear, threads get damage. Sand paper is a great way to randomly “scratch” the fabric. A low grain is better ( 240) but apply gently as it will easily rip through low weight fabric. Use it primarily on “edges”. You can also use thinner grain ( 600) to really dull the fabric colours.
Step 03: SWEAT //Everyone sweats: armpits, neck, lower back will be areas you will want to show some sweat marks. To make these stains, use a spray bottle and mix-in UNSWEETENED TEA and/or UNSWEETENED (INSTANT)COFFEE. Spray to taste. For large pieces ( tusken robes) you can also create a “tea Bath” and let the clothes rest in it for a few hours. You will still need to add stains in specific area BUT it will give a general vintage tan tone.
Step 04: WET DIRT //Mix flour, instant coffee, curry, cinnamon powder (all or any combination ) with water to make it slurry then apply as needed. You can also use shoe polish to emulate grease stains.
Step 05: DRY DIRT-DUST //Mix flour, instant coffee, curry, cinnamon powder ( all or any combination ) in a Nylon then blend it by tapping the “puff” onto the clothing. This will not stay if you wash your clothes of course.
FABRIC DYE //When I produce the clothing that will require weathering, I never search for the exact colour fabric, I tend to go one or two shades down because it will get darker through the weathering process. The first step is using a fabric dye very loosely. Forget what it says on the package; I take a big bucket filled with water ( at this point I don’t even care if it is hot) I dump the powder in it , mix a bit and then drop the clothes inside – I very roughly stir around , squeeze it with my hand and remove. The idea is that it will be IMPERFECT – I absolutely do not want it to be even at all. Some parts will be darker, some others won’t even get dyed at all and that’s great. let it dry outside on a line…
ACRYLIC PAINT //You can also use acrylic paints if you want to achieve very specific detailing; in that case do spray some water onto the fabric before applying, deep fabric will absorb the paint better. You can also use some spray cans/airbrush for additional shading of colours but it will stiffen the fabric.
USE A FLAME //With much care, you can use the flame to “burn” the fabric. Test first to see how it will react- some blend will go up in flame, the more natural one will react slower and better. Have water ready just in case and be sparse.
WD-40 //A great way to stain/age clothes the easy way is a can of WD-40. Spray around in the area most likely to get “sweat” – armpits, collar, belt area…
WASH ? WHY ? // I tend to smile when someone asks me if the costume can be washed after weathering. The more you wear the more naturally weathered it will look thus even more realistic; you would not want to wash that. I do understand the issue of potential “smell” this is why- regardless of the costume, I wear a compression suit underneath; it absorbs most of the sweat and odours. Hang your costume to dry naturally and if smell exists use some Febreeze or such.