FAQ

Why Timber Changes Colour

Exposure to Weather | Sapstain Mould | Bluestain Mould | Iron Staining

Earlier this month (May 2016), Preschem was asked to give a presentation on why timber changes colour at the Victorian Woodworkers Association. This got us thinking that this topic would make a great general knowledge post. After all, this will assist with some of those decisions on what to do when building something out of wood.

Why does timber change colour?

  1. Exposure to weather, including UV and rain
  2. Staining due to natural or introduced causes
  3. Chemical changes within the wood resins, or “extractives”
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Timber Properties and Decay

Timber Properties and Decay | Timber decay around homes

This article first appeared in the Professional Pest Manager Magazine June/July edition (Subscription only). Please note it was written with pest controllers in mind.

Timber decay around homes and properties is generally poorly understood by the general public. Pest controllers will inevitably come across decay that has been miss-diagnosed by the property owner as termite or borer attack. Thankfully, due to the internet, this is less of an issue now than it used to be, but sometimes a little information (from the internet) is a potential recipe for disaster. There is also no doubt that during the inspection process for a potential insect or rodent infestation, that the pest controller will come across decay. There would be hardly a premises in Australia that doesn’t contain it in some shape or form.

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Best Decking Oil Results

Deck Preparation before Oiling | Weathering timber

Previously, I have discussed the problems that people commonly have when they apply Aussie Clear to Merbau decking. As I stated in that post, to achieve the best results, deck preparation before oiling is essential:

  • once the deck has been installed, allow 6-8 weeks for it to weather
  • weathering of decks allows the resins, tannins, waxes and natural pigments (all called extractives) to bleed out
  • the weathering process also starts to open up the timber fibres

All of the points above mean you will be able to apply more Aussie Clear to the timber. Your first application of decking oil will last much longer.

All this theory is very good, but where is the proof in the pudding?

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Registered vs Unregistered Pesticides

Registration of Pesticides | APVMA | AgVet Legislation

I receive a lot of technical enquiries from the public about how to control timber decay. Mostly, it’s from someone have needs to repair an issue they have or wish to prevent it from occurring. There is one thing that crops up occasionally which is a concern; they sometimes mention they’ve heard of, or been recommended a product by someone. When asked the products name, I’ve never heard of it. A quick check on the APVMA’s Pubcris database often shows that it’s not a registered product! All products that are designed to kill another living thing are classified as pesticides under the AgVet legislation. So why is the registration of pesticides so important?

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Aussie Clear – Decking oil for all hardwood timber

Decking Oil for all hardwood timber

AUSSIE CLEAR and AUSSIE CLEAR LIGHT are Preschem’s range of decking oil for all hardwood timber. The philosophy behind this is that most hardwood timbers available in Australia are very similar in their properties. Even if their natural appearance are different. Thus a simple range of timber finishes will fit the bill.

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Timber preparation for decking oil or timber finishes

Timber preparation prior to oiling your deck

Deck Cleaner | Deck WashWhen you get around to reapplying your Aussie Clear decking oil after 9-12 months, there are a few simple things you should do before hand to ensure fantastic results. Penetrative timber finishes applied over a poorly prepared deck or any other exterior timber, will result in very poor results. Correct timber preparation prior to oiling your deck will ensure fantastic results.

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Timber Finishes – The new Radial Timber Sealer

wood finishes radial timber sealertimber finishes | timber treatment

Preschem has recently re-released it’s Radial Timber Sealer product. However, it’s a new high tech formulation from the ground up! This wood finish was originally designed for Radial Timber* projects, where the architect or customer wished the timber to weather off to that silver-grey look, while protecting it from the elements. As far as timber finishes go this is a specialist product and as such, may not be very well understood. Hopefully this post will explain clearly the features of Radial Timber Sealer. We’ll start at the beginning which means a quick lesson on timber and dimensional stability.

All wood has a natural moisture content. This moisture content varies significantly depending on a number of factors such as is it “green” meaning unseasoned through to being properly processed and dried such as kiln dried. Typically Australian Eucalypt timber that’s “green” has a moisture content (MC) as high as 80%. Kiln dried timber will be between 11-15%.

The significance of this is when timber changes MC it shrinks if it’s drying, but expands if it takes up moisture. Rapid changes in MC can cause issues such as warping, cupping, splitting and checking. What happens is the outer surface shrinks or expands rapidly, but the timber under that surface takes longer to change MC, so internal stresses are created. This is dimensional instability and is to be avoided where possible. When timber is processed from green to kiln dried, it is done slowly and carefully to avoid this. However, even timber that has been properly kiln dried can still have splitting and checking occur when its placed in a weather exposed situation, especially without any finish applied. The wood will still adjust it’s MC to its environment and this process is called seasoning. Seasoning will also cause dimensional stability issues.

Where the ultimate goal is to have the timber weather off to a pleasing silver-grey but prevent the issues of splitting, cupping and checking. You thus need a timber finish or wood treatment such as Radial Timber Sealer. Its key features are:

  • Once off application for newly installed durable timber, where the desired result is to weather naturally
  • Unpigmented and contains no UV agent so allows the timber to turn silver-grey
  • Clear finish formulated to control moisture and even stops wetting for around 6 months
  • Highly effective moisture control for 12 months allows the timber to completely season naturally
  • Contains a powerful mouldacide that prevents sapstain or bluestain moulds during seasoning

radial timber sealer will give you the natural weathered look

If you wish to maintain the timber’s “new look” rather than allow it to go grey, then the timber finish product to use is Aussie Clear for mid to dark toned hardwoods, or Aussie Clear Light for blond and lightly coloured timber. Exterior Pine Clear is the recommended product for Treated Pine.

* Radial Timber Sales is the wholesale/retail arm of Radial Timber Australia. Both companies are part of our wider business group. The Radial technology of cutting sawlogs is unique technology that allows very high yields from smaller plantation or new growth logs, while improving dimensional stability. Visit radialtimbers.com.au for more information on the technology and product profiles.

Which Wood Preservative for painted Timber Windows with rot? No Rot Gel.

wood preservative | window repair

One common question asked by the public is how to conduct a window repair when its affected by wood decay. The next question always is, what’s a suitable wood preservative when the window repair is to be painted over. The answer is quite simply: No Rot Gel.

Preschem No Rot Gel Wood Preservative

The cause of the wood decay, or dry rot is typically due to the paint system starting to break down by cracking or peeling. This allows moisture to get into the timber when it rains thus allowing the onset of timber decay. To remedy this it is recommended that you apply a suitable wood preservative such as Preschem’s No Rot Gel:

  • Strip or sand back the painted surface to bare timber around the affected section, preferably 300mm in all directions from where there is visible decay.This is advisable even if the rot is localised in one small section, as the fungi will be spreading via tendril like fingers that will be difficult to detect under the painted surface. The fungi will do this to spread elsewhere if the conditions are right. It’s best to knock it properly on the head the first time rather than have it causing you grief several years down the track, including the potential of having to replace the window frame entirely.
  • Dig out the dry rot carefully with a chisel or similar implement until you get to sound wood.
  • Dampen the timber with water
  • Apply No Rot Gel timber preservative as per the directions on the pack. Ensure that 2 coats are applied within 2 hours. If you leave it longer than that between the recommended two coats, you run the risk of the solvent drying, which means the second coat will not soak in. You can apply the second coat as soon as the first one has soaked in.
  • Allow the No Rot Gel to dry for about 24 hours
  • Use a suitable exterior timber filler to repair the cavity. Allow it to dry as per the manufacturers recommendations, then sand to a smooth uniform surface.
  • Paint over the repair with a quality exterior paint.

The advantage of No Rot Gel being used in this way is that it will kill and sanitise any dormant or active wood rot including the tendrils that are looking for another spot to grow. In addition, the timber preservative is locked in under the paint, where the boron active ingredient will remain there indefinitely, waiting for such a time where moisture starts finding its way back into the timber. Obviously if you’re properly maintaining your painting, then this could be a very long time indeed, as dry wood won’t rot.

Note: If you’re wanting a timber treatment for exterior use that won’t be painted over, then Timber Preserver is product to use.

For those of you who live within the Melbourne metro region and wish to have a tradesman come and do the work for you, then I recommend that you contact the Wood Rot Doctor to discuss your repair requirements on 1800 641 711 or visit the website at woodrotdoctor.com.au

Aussie Clear on Merbau decking

decking oil | timber finishes

One of the most common mistakes when people apply Aussie Clear as a decking oil onto new Merbau timber, is that people don’t properly read the application instructions. The instructions read: “allow new Merbau timber to weather for 6 to 8 weeks prior to applying Aussie Clear” and “… any excess oil remaining on the surface after 2 hours should be wiped off.”

Aussie Clear on Merbau Decking

Over oiled Merbau deck. Note the sheen which should not occur if Aussie Clear is correctly applied.

The reason for this is two fold:

1. Merbau is a very resinous timber.

If the timber is new then when you apply any decking oil product, those resins will mean you won’t get as much of the oil into the timber. It is preferable to allow it to weather for 6-8 weeks, or wash it regularly with fresh water if under cover for about the same period. It’s the water that bleeds the resins out of the timber. In other words, timber finishes work best when you allow the timber to weather. When you do this, your first application of Aussie Clear will be a proper “dose” and should last between 9-12 months (depending on exposure).

However, there is one exception to this where Preschem would recommend oiling the timber straight away, and that’s if the deck has been completed in the middle of a heat wave. In this instance, put one very light coating of Aussie Clear down immediately, as this will prevent the timber rapidly drying which can cause dimensional instability resulting in cupping, splitting and checking. However, this light application will not last all that long for the reasons explained above, so you will need to reapply sooner than what would normally be expected.

Over oiled Merbau Deck

Over oiled Merbau decking. Note the film is wearing off quickly.

 

2. Aussie Clear that hasn’t soaked in after 2 hours will form a semi-gloss film.

When applied correctly to a timber deck using a lambswool applicator, Aussie Clear decking oil will not form a film. If there is an excess on the timber, then that oil forms a film on the timber if it’s not removed with a clean dry rag. This film actually looks quite pleasing, so the common mistake is to keep re-applying the oil until its a “nice” looking finish. This film can occur with any timber, but is more likely to occur with new Merbau due to it’s high resin content.

The problem with this is that the film is not durable. It’s very easy to scratch and scuff the surface, which is a common complaint when this occurs. This is especially true on a hot day, as the coating softens significantly with heat.

Aussie Clear is designed to be a true penetrative matte wood finish. It will protect and enhance the timber through it’s proven formulation by:

  • protect against UV weathering
  • improve dimensional stability by controlling moisture content
  • prevent unsightly sapstain/bluestain moulds
  • enhance the natural beauty of timber season after season with regular maintenance