What chemicals to use on oiled ceder without expelling the oils

I am using SH to wash houses and i have 5 cedar cladding houses to wash and they have been oiled to protect the timber.
What can i use to get them clean without pulling the oil out of the timber?

My standard house wash mix is 2g SH 5g Water and i down stream.

Any help would be great

Troy,

Wow, a Kiwi on the site! New Zealand is the most beautiful country in the world.

Sodium hypochlorite onto the cedar at no more than 1.5% concentration, a bit of non-ammonia soap (say ~ 2 “squirts” per gal. of mix) works very well at protecting existing stain while cleaning the wood and killing any mold/mildew. If you have any surfactant, 1 oz./gal. of mix will give the mix “cling” on vertical surfaces and keep it wet a bit longer.

Washing is just a very good rinse. Very low pressure, and high water flow is best. Cedar is quite soft and easily damaged. Low pressure will also assist in keeping the existing stain intact.

Thanks for your advise, Is this mix designed for down streaming of application through a electric pump system.

Thanks
Troy
Wash Rite NZ
www.washrite.co.nz

Troy,

We only use 12V HVLP pump units to apply chemicals and stain. For most of our chemical applications, downstreaming dilutes the mix too much to be of use. An SH mix (using 12%) would possibly be the one exception. If you can get your dilution ratio down to 8 -1 downstreaming 12%, that leaves you with a concentration of SH coming out of the wand at 1.5%, which is ideal for wood. I’m not sure how soap mixes in straight 12%, but it better not contain ammonia. I would assume a straight surfactant would mix fine with a bit of stirring.