Sun Frog Born Again Brightener Concentrate Crystals- Important for reversing Tanin Darkening from age and strong Cleaner use on Redwood and Cedar, less important on Fir and Pines.  Apply to wet wood after Cleaning to bring back original natural wood color.  The better you make your wood look before sealing, the better it will look when sealed. Worth the money and effort on Redwood and Cedar!