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Paint spec for Iroko to avoid tannin bleed

Hi folks
I have an orangery to paint, its newly built with iroko wood and has been primed in albany acrylic primer undercoat. I went to look at it over the weekend and it has some severe bleed coming through. I was considering using zinsser cover stain tinted to the colour; a little greene grey.
Someone has advised the client to use a microporous system.
I was thinking that the use of albany primer undercoat would undermine any microporous system.
I will return later in the year to paint the exterior; any thoughts on best product for a) interior and b) exterior?
Any thoughts on the bleeding of the tannins in the iroko.


Aluminium leafing primer would work inside and out to hold back the tannin. Shellac based primer is an interior only stain block solution for this sort of job. Neither of these blockers are microporous. On the exterior you could old fashioned oil system, (I’d be interested if anyone has specific experience with water based system over Ally wood primer to suggest a non oil system?)

On the interior, you have the pick of the bunch for water based systems over BIN or Pegaprim

Just checking the Albany spec as Im not familiar with it, not wishing to cast aspersions on the previous advice for your client or on the people who primed the orangery, but if they read the Albany primer undercoat label it specifically says use Aluminium wood primer on hardwood. That cuts out the value of a microporous system.

See if Ben at paints and Interiors can chip in, he is clued up on the vagaries of microporous - in Sweden apparently it is a laughable idea, yet in germany it is the way to go…

Morning All!

The first point is by using and acrylic primer u/c there would be little point in putting on something microporous. For new timber i am very keen on using solid opaque stains/Lasurs. You can see the grain of the timber through them, but they are very easy to use - a first coat of a preserver, followed by 2 coats, and are easy to maintain - a quick light scour or rub down, followed by a single coat. They do however work best applied to bare timber.

Osmo Country Colour is a great product and is microporous. I comes in 18 basic colours and can be copied into any RAL coloutr of your choice although this incurrs an extra charge and a minimum order from Germany.

Other lasurs to mention are Scala Klassisk Oljefarg an oil based product from Sweden. Again this is a 2 coat system after a clear preserver. They also have a waterbased lasur called Solid V - a similar product to Superdec, and can be applied the same way.

I have no experience of it but Owatrols Solid colour stain is a similar beast to all these and waterbased, which may also be worth a look in and a linseed may alss be worth looking into. Done properly linseeds last for years, but again you need to start from bare timber for it to work best.

I have asked Osmo about the Tannin issue and their product and am awaiting a reply, but please do give me a shout and i will happily look into the others for you and see what we can come up with!

I have heard back from Osmo and they have issues with tanins and their Country Colour. Because their products are microporous the tannins WILL bleed through. They can be washed off with a fungicidal wash, but that would be a little tricky on an Orangery roof.

By the sounds of it avoid tannin rich timbers and microporous all together as you will get bleed through.

I wonder now whether you should go with something like a Zinsser Coverstain as their literature says it will block cedar and redwood bleed(maybe ask them about Iroko too), followed by either a high spec oil or waterbased system - up to you.

If i can be of help let me know.

About 15 years ago I was sub contracting to a company who had on a VERY BIG conservatory.
It was about 45k’s worth and they were going to use it for a gym - you could have put a swimming pool in there it was that big!
Hardwood (don’t ask me which one) construction onto a dwarf wall that came with a full painting spec from the manufacturers.

Spec was a full clean down followed by ali primer, 2 x undercoats followed by 2 x gloss white in dulux weathershield to match the rest of the house.

About 6 months later the whole of the exterior was failing and you could remove the paint system in sheets with a scraper. The ali primer hadn’t adhered to anything.

After much passing the blame from the manufacturer to the decorating company it was decided to go with opaque wood stain.

Once the timber was taken back to bare timber,a coat of wood preserver followed by 3 coats of Johnstones opaque white woodstain ( all solvent based) was applied.

No problems with tannins and a maintained painting cycle of 1 coat every 3-4 years.
Never heard of any more problems after that and the finish looked great.

Would have thought you could get a little greene grey closely matched to an opaque woodstain by Johnstones or who ever else does a solvent based finish.

Thank you all for your input, much appreciated.

Andy do you not think covastain would do the job then? You know I have a resistance to using the shellac based primers having found they are so fast on drying that its hard to keep a nice finish and the cleaning of brushes I have found can be problematic.
If cover stain will perform the same function I feel it more friendly to use.

Coverstain primer and complete with oil system on top sounds favourite for the tannin solution. Have you checked for adhesion of the waterbased primer?

I would suggest samples, to prove that it is going to work before tackling the whole job? Jumping in on an educated guess, never a good idea, especially as you havent created the difficulty in the specification ie by applying a simple water based primer on iroko, the joiners went against the recommendations of the primer company.

Interesting about the Johnstons. It may be the case that products like the Osmo which are now using natural oils, may not be up to holding back the tannins as the older fashioned Opaque stains like the Johnstons. I have looked at Solignums Architectural (Oil based) data sheet and they appear to be fine with hardwoods,not mentioning any tannin issues, only citing that with Iroko, Teak and the such like, the drying times may increase.

I am going to look into this and see if i can find the best of both and will report back. It may be that th Swedes know a thing or two!!

Best paint for hardwood timbers according to my Swedish Supplier

It is a tung oil, Silicon Alkyd mix. The tung oil penetrates the hardwood and feeds it with the silicon modified alkyd protecting the surface.

Not sure on price, but availability is order only and this could take up to 6 weeks depending on when i could add to an order.