OXcon: Blonding AgentDescription OXcon Blonding Agent OXcon (oxalic acid concentrate) is a powerful blonding agent that brightens wood surfaces and returns gray, weathered wood to a fresh, clean appearance. OXcon will also remove rust stains from around nails, spikes, and screws. Use OXcon on logs, decks, porches, railings and other weathered wood surfaces. OXcon comes as a concentrate that is diluted with water prior to use. It is best applied using a garden type pump up