One of the biggest problems today facing vintage cap collectors besides stiff or broken visor boards is mold & mildew. This happens if the cap is stored too long in a warm and humid area. I receive vintage caps with this problem every so often. Since many of these caps are priceless or very hard to replace, I thoroughly clean them rather than throw them out. Here is my tutorial on how I remove mold & mildew on caps.
Supplies: You will need disinfectant wipes and isopropyl alcohol, the strongest you can get. Mine was 99%. If you get sick easily, perhaps you will need a hospital face mask. You can get all of these at your local drugstore.
First, look everywhere on the cap for any signs of mold or mildew. On the outside it may appear as powdery-looking spots. On the inside of the cap and the outer area of the sweatband, they may appear mostly in black, white, and green-ish spots or a larger powdery area or layer.
If you spy plenty of it in plain sight, prepare for an unpleasant surprise on the back of the sweatband! What a sight it was inside this cap! This is where most of your mold & mildew is going to be.
Take out your disinfectant wipes. I take one and fold it to make it thicker. You may want to dab first on any outside areas that may have mold & mildew. Smoothly wipe it along the outer sweatband. The mold should wipe away easy and leave a clean surface. Now do the same on the inside. If it is a leather band it should be moist enough to fold back without damage. If not, be careful or do not attempt if you are uncomfortable with doing so. Make sure you get in-between the leather and the white fabric. Get the other side of the white fabric as well. Then wait for the cap to dry, it shouldn’t take too long. Check it when it’s dry, there should not be a trace of mold left.
I use the 99% isopropyl alcohol to make sure the mold & mildew goes away for good. Plus, it gets into all the places you can't reach with the disinfectant wipes. It also dries fast which reduces the chances of shrinkage of the wool. NOTE: DO NOT USE ALCOHOL IF THE CROWN AND VISOR ARE DIFFERENT COLORS OR ELSE THEY WILL BLEED INTO EACH OTHER. Only use alcohol if the cap is all one color. Also keep the alcohol away from the embroidered logo as the color will bleed into the logo. I pour a small amount on each area that has the mold & mildew. In this case, there were areas on the visor and crown. I then poured some on the bottom outside on the other side of the sweatband area which was where most of the mold was.
Now it is time to let the cap dry. Take any normal precautions you would with any cap to prevent shrinkage. Wear it until its dry if you feel comfortable doing so or just let it sit. Any little white specks that rubbed off from the disinfectant wipes' fabric can be removed with tape.
The mold smell will persist even after cleaning. I recommend dryer fabric softener sheets to reduce the smell. Put one inside the cap and try to cover as many eyelets as you can and then fold the cap in. Change them every few weeks and eventually the smell will start to fade. That’s about all there is that you can really do about it unless someone else has a better idea! Make sure you wash your hands after or better yet take a shower. If you are storing your cap in a box or container of some kind, you should put a package of silica gel in there with it. That’s everything!
DISCLAIMER - I am not responsible for any shrinkage, damage, or any other problem with your cap if you attempt this. There is also a chance this can make you sick. This is what has worked for me; it may or may not work for you. Try at your own risk. Do not attempt if you are prone to illness or have any medical conditions that may be affected by it.