Using Napisan to Clean Your Deck: Pros, Cons, and Complete How-To Guide

(Deck Rejuvenation — Melbourne’s Timber Restoration Specialists)

Melbourne’s decks cop it all — hot summers, cold wet winters, and that classic sideways rain. If your timber’s starting to look dull, greasy, or just tired, you’ve probably heard people suggest using Napisan to clean it.

Good news: it works — but only if you do it right.
Here’s a complete guide on when to use it, how to mix it, the vital follow-up acid step, and the safest way to bring your deck back to life.

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1. What Is Napisan and Why Use It on Decks?

Napisan (and similar laundry soakers) contain sodium percarbonate, which releases hydrogen peroxide when dissolved. That oxygen reaction lifts and removes organic grime like mould, algae, old oils, and tannins.

It’s the same active ingredient found in many deck cleaners — just at a fraction of the price.

Used correctly, Napisan can clean and strip old oils from your timber, helping it absorb fresh coating. Used incorrectly, it can darken timber and cause coating failure.

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2. When and Why We Recommend the Napisan Method

At Deck Rejuvenation, we typically recommend this method for DIY homeowners who:

• Want to save money on deck prep products,

• Don’t have the budget for a full professional restoration,

• Or want to safely refresh solvent-based oils before re-coating.

This process is particularly effective for removing traditional solvent-based oils such as Cutek CD50 or similar penetrating coatings.
Napisan helps draw out old oils and natural tannins, leaving a clean surface ready for brightening and oiling.

💡 Note: This process does not work on water-based decking oils or membrane coatings such as Sikkens Decking Oil.

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3. How Napisan Works on Timber

When mixed with water, sodium percarbonate releases hydrogen peroxide. This chemical reaction:

• Breaks down old solvent oils and organic build-up,

• Draws out deep tannins, and

• Kills mould, mildew, and algae.

It’s like giving your timber a deep oxygen facial — stripping out contaminants so it can breathe again.

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4. Pros and Cons of Using Napisan

✅ Pros

• Affordable, accessible, and easy to use.

• Effective for solvent-based oil removal.

• Eco-friendlier than harsh chemical strippers.

• Ideal pre-step before oiling.

❌ Cons

• Doesn’t work on water-based or membrane coatings.

• Will darken timber if not neutralised immediately.

• Must be followed by an acid wash to balance pH.

• Overuse or strong concentration can roughen fibres.

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5. Step-by-Step: Cleaning Your Deck with Napisan

🧰 What You’ll Need

• Napisan (or generic sodium percarbonate)

• 9 L bucket of warm water

• Hard-bristle brush or broom

• Garden hose or low-pressure washer

• Gloves, goggles, and old clothes

⚙️ Mixing Ratio

Dissolve around 500 g of Napisan per 9 L of warm water.
Warm water helps it dissolve fully and activates the cleaning action faster.

🪣 How to Apply

1. Pre-wet the deck if it’s bone dry.

2. Apply the Napisan mix evenly using a brush, mop, or garden sprayer.

3. Let it sit for about 10–15 minutes — keep it damp, don’t let it dry.

4. Scrub with a stiff brush to loosen old oils and grime.

5. Rinse thoroughly with clean water or a low-pressure washer.

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6. Acid Neutralising Treatment — Must Follow Immediately After Napisan

This step is non-negotiable. Napisan is alkaline and will darken the timber if left untreated.
The acid neutraliser (usually oxalic acid) brings the timber’s pH back down, brightens colour, and prevents coating problems.

You must do this straight after rinsing the Napisan — while the timber is still damp.

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🧪 What You’ll Need

• Oxalic acid crystals (2 kg costs about $34 AUD — see shopping list below)

• Warm water

• 9 L bucket

• Mop or garden sprayer

• Hose or pressure washer

• Gloves, mask, and goggles

⚙️ Mixing Ratio

Add roughly 200 g (about one mounded capful) of oxalic acid crystals per 9 L of warm water, stirring until dissolved.

🧴 Application Steps

1. Pre-wet surrounding areas (paint, render, glass, stainless steel) to avoid bleaching.

2. Apply the acid evenly with a mop or sprayer, covering every board.

3. Let it dwell for 15 minutes. You’ll see the timber start to light up as it brightens and metal stains fade.

4. Rinse extremely thoroughly — use lots of water or a pressure washer.
   Any residue left behind can interfere with your next coat of oil.

💡 If you want your deck even brighter, repeat the acid step once more after rinsing and drying.

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⚠️ Safety Tips

• Don’t let the acid sit on stainless, render, or painted areas.

• Always hose before, during, and after use.

• Keep pets and kids clear until fully rinsed.

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7. Timing and Next Steps

Once the acid rinse is complete, let your deck dry overnight.
By the next morning, it’s ready for oiling — assuming the weather is dry and warm.

⏰ Do not delay oiling:
Every day you leave the bare timber exposed, it darkens and begins absorbing airborne contaminants.
If you wait too long, you’ll need to repeat the entire cleaning process.

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8. Common Mistakes to Avoid

• Waiting days between Napisan and acid treatments.

• Skipping the acid step entirely.

• Using Napisan on water-based or membrane coatings.

• Leaving chemical residue before oiling.

• Oiling too soon (before the deck is completely dry).

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9. When to Call the Pros

If your deck has flaking coatings, extensive weathering, or persistent mould, it’s best to bring in specialists.
At Deck Rejuvenation, we use professional systems — sanding, neutralising, and oiling — to restore decks properly and set up easy long-term maintenance.

But if you’re confident doing it yourself, this Napisan + Oxalic Acid method is hands-down the best DIY approach to rejuvenate solvent-based decks safely and affordably.

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10. Final Word

This process isn’t a miracle cure — but done right, it delivers professional-grade results without the professional price tag.
Follow the steps, respect the timing, and finish with a quality decking oil — your deck will look new again and stay that way.

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🛒 DIY Shopping List

Here’s what you’ll need to complete the full Napisan + Acid clean:

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✅ Deck Rejuvenation — Melbourne’s Timber Deck Restoration Experts
We’ve spent years testing products and refining processes for our climate. Whether you’re a DIYer or want it handled start-to-finish, we’ll keep your deck protected year-round.
Get in touch to book your professional restoration or maintenance visit.

thwhile. The oil will preserve the wood from rain and also serve as a wonderful color stain, so it will be able to resist stormy weather.

Request advice and inspections from skilled local decking installers who can do your tasks affordably and in the best possible way. Our team is willing to help and do the work for you. Please check-out our recent works http://deckrejuvenation.com.au/ and call us via 1300-363-478.

Until next time!

Deck Rejuvenation Pty Ltd Team