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Understanding SiOO:X coating and its transformative Impact on timber

SiOO:X coating stands as a versatile solution in timber treatment, a protective layer designed to enhance and preserve wood surfaces. Unlike traditional coatings, SiOO:X penetrates deeply into the timber, offering durability and weather-resistance. Its unique formulation allows it to activate upon exposure to moisture, making it particularly effective for exterior applications where timber is constantly exposed to the elements.

If you are looking to understand the transformative effect that SiOO:X has in terms of appearance and surface protection, here is what will be covered in this blog:

Let’s get into it!

What is SiOO:X?

SiOO:X clear-coat Cladding protection is a transformative, two-component wood treatment renowned for evolving into a natural grey hue, providing internal wood surface protection. Its patented silicate formula interacts with humidity, dryness, and CO2, gradually developing colour and protective attributes over time.

SiOO:X coating offers deep penetration, durability, and weather-resistance, activating upon moisture exposure. This makes it ideal for exterior timber exposed to elements, enhancing and preserving natural timber surfaces.

SiOO:X is a two-part system. Part one is a solution that penetrates the fibres of the timber, forming a flexible network of crystals. This creates a barrier strengthening and protecting the timber.

Part two of the system contains silicone in the form of a water-based emulsion, designed to create a breathable water repellent layer. This is applied to bond with part 1 and effectively seal the surface of the timber.

The re-application of part two of the system for maintenance, will vary project to project.

Advantages of SiOO:X coating

SiOO:X coating boasts numerous advantages, making it a standout choice in timber protection.

  • It has a deep penetration capability, making it a great option for exterior applications that are exposed to the weather.
  • This coating speeds up the timber weathering process whilst protecting timber. When exposed to the weather, SiOO:X will evolve into a beautiful grey/silver hue overtime -mimicking an aged appearance. Usually architectural timber will weather unevenly. This weathering will depend on the timber species used, the project design, the location of the project and the location of the timber.
  • Once applied to timber, SiOO:X provides the solution to uneven weathering. A uniformed weathered look across all the timber pieces will occur over the period of months, following application. The clean, smooth and silver-grey tone will be achieved across all pieces of external timber, regardless of where it was installed.
  • SiOO:X’s formulation acts as a barrier against algae, mould, and wood rot, offering long-term preservation while embracing an environmentally friendly approach.

Mortlock’s recommendation when it comes to SiOO:X coating

At Mortlock Timber, we want to help you achieve a high quality weathered look on external timber cladding using SiOO:X coating. While it is versatile and suitable for various wood types and construction techniques, it is essential to know how to use and control this coating effectively.

What we do in terms of SiOO:X coating 

The timber is pre-coated with the SiOO:X Weather two-part protection system by Mortlock Timber prior to delivery. Mortlock Timber applies three coats in total. Two coats of SiOO:X part one and one coat of part 2.

The timber is completely dried before the second coat is applied. We primarily coat two timber products, our Trendplank and Proplank systems.


At Mortlock Timber, we opt for using band sawn or brushed over dressed timber for better coating penetration. A band sawn textured finish is used to enhance coating absorption in all timber species for improved performance. We recommend SiOO:X should be sanded in a 60 – 80 grit range, when required.

Maintenance with SiOO:X coating

A maintenance re-coat is recommended every 5-6 years. However this product can last up to 10-15 years without maintenance.

To speed up the process or cause the timber to weather in non-exposed areas, lightly spray the timber with water once coating has been applied every day for 2-3 weeks. The moisture will react with the coating to ensure an even silvering on the surface.

You need to avoid applying to dressed surfaces as mill glaze resists penetration and can go patchy.

If the surface is scratched or cut, exposing untreated wood, apply two coats of SiOO:X Wood Protection and seal it with SiOO:X Surface Protection. For more information pertaining to different degrees of cleaning, refer to the SiOO:X wood protection care and maintenance guidelines here.


To clean SiOO:X coated surfaces, apply a diluted SiOO:X Maintenance Wash with a soft brush, wait 20 minutes and then gently apply again. Be sure to rinse thoroughly and leave to dry.  

Where to use SiOO:X coating

We advise not to use SiOO:X on decking as the coating is easily removed when walked on.

In terms of using SiOO:X for internal applications, the coating won’t grey off. It is designed for exteriors where the timber is exposed to the weather, as it relies on the moisture to active it.

Choosing the right timber species for SiOO:X

We recommend SiOO:X is best utilised with thermally modified timbers such as vacoa, malvec and burnt ash. Thermally modified timber treated with SiOO:X coating stands out as a superior choice for several reasons.

Firstly, the thermal modification process eradicates the issue of high tannin content often found in Australian hardwoods, ensuring a tannin-free wood surface. This absence of tannins eliminates the common staining problems associated with such timber types.

Secondly, the thermal modification produces a timber softer than Australian hardwoods such as jarrah, spotted gum and blackbutt. These have a high tannin content and have a dense structure which makes it harder for coatings to penetrate the timber surface. We recommend against using SiOO:X with blackbutt and ironbark timber.

We have also found that SiOO:X on pacific teak will exhibit an unwanted green colour, as it will react to the tanning and will leach everywhere. We recommend not using SiOO:X with pacific teak timber.

Moreover, the application of SiOO:X coating not only stops tannins from leaching but also utilises a brushed approach that facilitates deeper penetration into the timber boards.

The combination of thermal modification and SiOO:X coating thus presents a winning solution, offering enhanced durability, reduced staining issues, and improved aesthetic appeal for timber products.

burnt ash fine sawn sioox
Fine sawn burnt ash coated with SiOO:X

Your vision, our expertise

The lifecycle of your materials is an important factor to consider when designing for long term beauty and durability. If you are planning on embracing the weathered look for your exterior cladding, our team can offer expert advice to ensure you get the best results with SiOO:X. If you are unsure about which coating you require for your project and SiOO:X does not sound like the correct option, be sure to inform yourself with the other coatings in our range.

With our wide selection of timber species, you are certain to find something that will fit your space’s requirements. Whether you are looking for timber battens or timber cladding, we can help you choose the best species, finish, and profile for your project.  Get in touch today for more information regarding our architectural timber products or to request a quote. One of our friendly team members will be happy to assist you!

View our pricing and product guide

For in-depth information about the range of products we offer, please fill out the form below to download our Architectural Timber Pricing and Product Guide. Inside you will find illustrations, specifications, portfolio photo examples and a hardwood timber price guide to assist with budgeting.


    Mortlock Timber

    We are committed to bringing you timber products that add value and endure for years to come, even in heavy traffic and harsh weather conditions. We understand the value of efficiency when it comes to installation and keeping hardwood timber costs down. That’s why we’ve spent decades perfecting our designs to make them easier to handle, less wasteful and more efficient to install. This efficiency allows us to offer you premier products that are more cost-effective so that you can experience greater savings on timber wall costs, timber ceiling costs, timber cladding costs and timber decking costs.

    Download our Pricing and Product Guide for our complete hardwood timber price list including timber decking prices, timber wall prices, timber ceiling prices and timber cladding prices.