I've seen some people talking about how to cover carboys to keep out light and it got me thinking. I found a can of "Flexseal" at my local CVS store and gave it a try. I left the top area clear and a strip down the side to aid with racking. Flexseal is basically a rubber compound that sprays on nicely and occludes light in one pass. I think it is superior to a cloth covering as it also will provide some "bump protection."
If you plan on doing it, use masking tape to cover whatever you don't want sprayed. I wrapped the neck and covered the opening. I used one strip of masking tape down the center to leave it clear too. One important point, be sure to remove the masking tape before it dries. This stuff dries very hard and you won't be able to pull it off once it's dried. I did this to one demijohn and one carboy so far. I will let you know how I like it as time goes by.
If you plan on doing it, use masking tape to cover whatever you don't want sprayed. I wrapped the neck and covered the opening. I used one strip of masking tape down the center to leave it clear too. One important point, be sure to remove the masking tape before it dries. This stuff dries very hard and you won't be able to pull it off once it's dried. I did this to one demijohn and one carboy so far. I will let you know how I like it as time goes by.