A method for the reduction or prevention of tannin-staining on a surfacesusceptible to tannin-staining through the use of a complexing agent fora transition-metal ion and compositions containing such a complexing agent

Abstract From the Canadian patent

Discoloration of surfaces, such as painted or treated wood surfaces, by tannin-staining caused by the complexing of certain transition metal ions with tannate ions (the process is often referred to in the art as "tannin-stain bleed") is reduced or prevented (eliminated) by contacting a transition natal ion on a painted surface or surface to be painted with a complexing agent for the transition metal ion, such as by the addition of the complexing agent for the transition-metal ion to paint formulations or by pretreatment of the wood surface with the complexing agent before painting. It is believed that the complexing agents form coordination complexes with transition-metal ions on the …