MITRA Forum Question Details

The active ingredient in Chloraseptic is 1.4% phenol or carbolic acid, which is an age old material used to inhibit mold and bacteria growth in non-food substances. Natural Pigments offers a 5% solution of phenol in a spray bottle (called Phenol Spray) that can be applied to traditional gesso and chalk grounds if one intends to store for some time. We have found it effective to prevent mold growth for up to 30 days, if the ground is stored in a sealed container in a refrigerator and Phenol Spray sprayed over the surface of the ground with a light spray every few days. It can also be applied to pigment pastes to prevent mold growth.

The advantage of using Phenol Spray over Chloraseptic in art is that it does not contain all the other ingredients found in the throat spray: FD&C Red #40, flavors, glycerin, purified water, sodium chloride, sodium citrate, sodium saccharin, sucraloseat. Phenol Spray is 5% phenol and the remainder is purified water and a small amount of glycerine. 

​Thanks for the quick response George.

​In my experience, denatured alcohol is usually effective for use in pigment pastes.  Several years ago, a Utrecht paint chemist recommended original Lysol disinfectant spray to retard mold growth in jars of acrylic dispersion paints, grounds, mediums etc. It is effective, and the active ingredient is commonly used as an antimicrobial in the paint industry. I really like the idea of that phenol spray, though- the smell of Lysol is pretty unpleasant! 

I have not felt the need to add anything to gesso or chalk glue grounds as long as I keep them in the refrigerator when not in use, even in classes where many students have access. I do always use denatured alcohol in aqueous pigment pastes. Bone black and some ochres still develop mold after a couple of months. I will likely give phenol a try this fall when I again teach true fresco, egg tempera, and distemper in my classes.