Alkali cleaner vs acid cleaner. What cleans what? Do I need both to clean my timber deck?

The quick answer is yes, because of the nature of timber contaminants, seen or unseen, that accumulate in your timber. An acid-based cleaner like Equisol Vitalise removes mineral-based stains. An alkali-based cleaner like Equisol Prime removes oil-based stains.

Most decks have both types of stains.

Existing timber traps a lot of surface contaminants such as grease, bird droppings, tracked dust and dirt, pollen drift, road grime, organic matter that deposits oil residue (leaves, blossoms, twigs, etc), ‘rusty’ water from rusting deck fixtures, garden chemical overspray, and more.

New timber can have mill glaze or contaminants picked up during shipping or storage.

The list of stuff your timber is exposed to is almost endless, depending on where you live. There’s salt spray near the ocean, airborne fungal spores in tropical areas, pollution-bearing rain in big cities that is contaminated with sulfur dioxide and nitrogen oxides, roof water runoff leaching heavy metals and VOCs, agricultural pesticides in farming areas, micro plastics, and even iron-rich sand in outback areas. We could literally go on for pages.

Equisol Pro E365 is a penetrating oil that allows timber to breathe and let water in and out. It is not a film, so it doesn’t act as a ‘plastic’ coating that contaminants sit on top of.

Even a deck with a film coating can let many of these contaminants penetrate into the deck, especially if the film coating is failing or cracked. Often decks have had multiple finishes under the film coating as well, such as old oil, which many cleaners cannot remove.

In short, your timber deck is a giant petrie dish, and there is no way of knowing exactly what is on, or in, there! 

One simple cleaner will not remove everything. Every woman who has ever cleaned makeup off her face will tell you that!

Faced with this uncertainty about what you are actually cleaning off your timber, using both an acid and and alkali-based will always remove more.

It’s time to get technical.

Alkali cleaner or acid cleaner?

A good rule of thumb is alkali cleaners remove acid-based stains, and acid cleaners remove alkali-based stains. Basically, use the opposite PH of your stain.

Alkaline cleaners generally remove oil-based stains through saponification, which breaks down the bonds within oils and fats.

Equisol Prime, with an alkaline pH will help remove oil-based marks on timber, like:

  • BBQ fats
  • Grease
  • Bird droppings
  • Pet faeces
  • Old decking oil
  • Tannins
  • Food and beverage spills, such as wine, coffee and juice
  • Organic residues, such as dirt, mould stains, plant matter, leaf marks, sap stains, etc
  • Motor oils

Acidic cleaners break down and dissolve the mineral compounds in inorganic stains.

Equisol Vitalise, with an acid pH will help remove mineral-based marks on timber, like:

  • Inorganic deposits
  • Pool chemical build up
  • Iron oxide stains, also known as black stains
  • Efflorescence (salt-based deposits)
  • Limescale (calcium-based deposits)
  • Rust
  • Hard water (high mineral deposits)
  • Salt, including coastal salt spray
  • Starch-based stains
  • Soap scum

The above is not a complete list, nor is it absolute. There are some items that fall into either category or move between them based on their PH level. Pet wee (uric acid) and some oils including vegetable, cooking and petroleum oils can be either acidic or alkaline, and require a combination of cleaners.

Most cleaning/brightening solutions on the market are oxalic acid-based, and excellent at removing a lot of the dirt on your deck. They also brighten the timber again so it looks fresher.

But some of the more gnarly contaminants require an alkali-based cleaner, like grease, BBQ fats, old oil, and tannins caught in the timber.

Wherever possible we recommend using them both, because we simply don’t know what is on the timber, or even sub-surface, that cannot be seen.

Sure, you can use just one and plenty of people opt for only the oxalic acid, but why would you leave stuff trapped under your new deck coating or oiling? It’s just going to reduce your coating’s effectiveness at protecting your timber, and increase the chances of timber decay. Plus, your maintenance cycle will be shorter. It’s kind of a lose-lose-lose.

The best timber longevity is all in the preparation and a combination of the two cleaners is optimum to remove as much as possible so you can enjoy your timber deck for many years to come.