Wood cleaners generally formulated using detergents for dirt removal and liquid bleach for mildew removal. However most of these cleaners have found to be not very effective for wood deck cleaning applications. For wood deck cleaning applications, specialty cleaners are available in market, which can be categorized into 3 main categories :
- Chlorine bleach based cleaners
- Oxygen bleach based cleaners
- Oxalic acid based formulations
Common types of chlorine bleach cleaners formulated for deck cleaning applications are made using sodium hypochlorite, calcium hypochlorite and dichloroisocyanurate. The first two are generally used laundry detergents while dichloroisocyanurate is a swimming pool additive. These chemicals have proved to be effective against mildew but do little to remove dirt or other surface deposits. However when used on wood decks, chlorine bleach based cleaners can do more harm than good, as it may result in the woods' having a whitish unnatural tone because of the bleaching out of natural components. In addition, if chlorine bleach based cleaners are not rinsed properly, the residue of chlorine salt may result in the premature aging of wood from the action of sunlight.
Oxygen Bleach Based Wood Cleaners
Oxygen based wood cleaners are formulated using disodium peroxydicarbonate, which is commonly known as sodium percarbonate. Sodium percarbonate is a powder, which when added with water forms hydrogen peroxide (a common oxygen bleach and soda ash). Hydrogen per- oxide is typically used as disinfectant and as a stripper for hair coloring applications. For wood cleaning applications, the oxygen bleach based cleaners have found to be effective in removing the mildew stains and the weathered gray residues from UV degradation. The sodium carbonate functions as a built-in detergent, which removed dirt and other deposits. Thus, sodium percarbonate based wood cleaners are effective in removing dirt, mildew and weathered gray residues. The cleaner can be used to treat the wood to make it return to its original appearance.
Oxalic Acid Based products
Some wood species like cedar and redwood contain natural resins known as tannins. These are water-soluble materials that are reddish brown in color. Water can extract these resins from the wood and deposit them on the surface thereby causing brown or black discoloration. Tannins can also react with iron present in nails or fasteners, which can result in blue-black stains. Neither oxygen bleach nor the chlorine bleaches are effective against tannin stains or iron stains. Oxalic acid based cleaners on the other hand, solubilizes iron stains and tannins and renders them colorless.
Hence, we can say, the oxalic acid based wood cleaners are materials of choice for application on redwood or cedar. However, oxalic acid is not an effective agent against mildew. Due to this reason, such type of woods is cleaned with a sodium percarbonate or chlorine based cleaner and follows it up with an oxalic acid based cleaner.
Sometimes, in order to restore a wood deck and prepare it for refinishing, the earlier finish - or what is left of it should be removed. Most wood cleaners and restorers are nor effective in removing stains or paints. This can be achieved with this application of chemical paint strippers.
Chemical paint strippers are typically based on organic solvents and caustic salts, such as sodium hydroxide or sodium meta silicate. Majority of these strippers is highly potent and requires extra care in their usage and handling. For example, contact with skin or eyes should be avoided. Suitable protective clothing and equipment must be worn or as given on the product label.
Depending on the formulation, paint strippers can be used to remove oil-based stains, varnishes, latex stains and paints.
Any residues of the paint strippers should be thoroughly rinsed from the wood before applying any other product to the surface, as any leftover residues of caustic salts can interfere with subsequently applied coatings.
Some manufacturers formulate their paint strippers with thickening agents to make the liquid cling better to vertical surfaces. This action improves the performance since it increases the contact time between the surface being treated and the active ingredients.