Black Tallowwood Deck

[Tim Luke]

Can someone help me with the above problem. I have tried to re-coat my deck which is only about twelve months old and it seems to be quite black in places. Is this mould and do I just have to use a Timber clean product or is it tannins in the wood.

I used Wattyl decking oil. And another thing am I better off using a water based finish in future that might pentrate the wood easier.

Thanks

[brynk]

gday tim luke

your black stuff could be metal dust which has reacted / rusted with the timber, oil & the recent rain. this happened recently on our deck - i set a mate up with a grinder near-by & the next time it rained (that arvo) there were all these little black spots everywhere. suffice-it-to-say, i was none too pleased. i'm hoping jimj's method of cleaning will lift the black spots, otherwise i will be sanding it.

in regards to the acrylic sealer: i loathe these coatings for external (and even internal) applications but that is my personal preference. the coating will eventually fail in a patchy fashion, wear faster in areas of higher traffic, etcet. not sure if you can recoat successfully before the coating itself fails (other memebers may be able to advise better) as i have had no experience - my bias towards oils has kept me away from them. finally, if you don't like the results of an oil, let it deteriorate then use a different product next time (say, 12 months at most, depending on where you live); if you don't like the results of the acrylic you are sanding it or waiting for a long time

something else to consider - you must seal both sides and end-grains of the timber for best results. this will ensure even moisture uptake & loss and limit warping. sealing only one side will still allow the underside to take on moisture. maybe there is an acrylic coating that will allow moisture to pass through it?

the attachment is a doco from the ironwood website which has some great info. http://www.ironwood.com.au


regards
brynk