What cleaner should I use before I apply a maintenance coat of stain?
First things first: yes, you should clean your home before you apply a maintenance coat of stain. You need to remove dirt/dust, pollen, bird poo, mold, mildew, and other surface contaminants. Start with a clean surface.
Before you start, do a couple of things:
1.) Test your cleaner in an inconspicuous area to make sure you won't damage the stain or cause discoloration.
2.) Protect your home's fixtures and surroundings from the cleaner. You don't want to bleach your plants. (Unless, of course, you really hate that bush and need an excuse to get a new one...)
Here are pros and cons to four popular cleaning products. This isn't an exhaustive list, so if you have additional questions, feel free to contact me.
Strongly bleaches all types of wood
Must be fresh in order to work (Check the date code. Make sure it's no more than 3 months old.)
Chlorine gas (which can be fatal) can be released if chlorine bleach is mixed with other household chemical
Readily kills plants, especially new growth
Very corrosive to metal fasteners, such as nails and screws
If not completely rinsed from the surface of the wood, it can continue to degrade the wood, as well as degrade any coatings applied
Oxalic Acid (Often on the shelf under a "deck stripper" or "deck clearer" label:
Particularly good at removing tanning stains
Will not discolor high-tanning woods like redwoods
It is the best product for removing rust stains
Works well to remove many types of coatings (paint and stain)
Does not kill mildew or mold
If not thoroughly rinsed from wood, will degrade any stain applied over top
Often need to be followed by a secondary neutralizing agent (like baking soda)
Sodium Percarbonate Bleach (Oxygen Bleach):
Most environmentally-friendly cleaner
Disassociates into hydrogen peroxide, soda ash, and water - all fairly benign
Will not aggressively corrode metal fasteners
Will not degrade coatings if small amounts left in the wood
Kills mold and mildew
In the right strength, will brighten and clean most wood
Will discolor high-tanning woods like redwood and some cedar
More expensive than other cleaners
The residual soda ash can appear as whitish patches underneath a stain or lacquer if not well rinsed.
Trisodium Phosphate (TSP):
Excellent for cleaning dirt
No bleaching action. Won't kill mold, mildew, or brighten wood
Any phosphate residue left behind can stimulate surface mold growth (It is important to thoroughly rinse.)
Published on: March 21st, 2018
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