Cleaning cedar siding

[Woodschild 14]

The last time (2002) I cleaned, brightened and sealed my cedar siding, I used a homemade bleach, water, Tide combination that I gleaned from this forum. I used Wolman to brighten and Ready Seal to finish. I was very happy with the results. Since that time, I have followed all of the talk about oxygen bleaches. I am wondering if I should change my cleaner this time. If so, can anyone recommend a product or a formula to use? Many thanks for all of the shared expertise. I have learned so much from all of you.

[plainpainter 217]

I wouldn't change

[RPetry 564]

The last time (2002) I cleaned, brightened and sealed my cedar siding, ... and Ready Seal to finish. I was very happy with the results.

Pamela,

It has been 9 years since you last stained the cedar? If so, disregard the previous advice. We have been using Ready Seal for a full decade now.

For cedar siding, a light strip will be best. Store purchased NaOH wood stripper or "sodium hydroxide" can work well. Just dilute from the instructions by adding 2 times the recommended water volume. You want a very light stripper to clean and get rid of any remaining Ready Seal stain or cedar tannin.

Allow to dry and inspect. If there are traces of mold/mildew, a 1.5% bleach wash will do the trick. If otherwise, ignore the bleach. Purchase some oxalic acid at your local paint store and mix at ~ 6 oz. volume per gallon. Spray or mop on, and allow the cedar to dry for a few days. Hit the cedar with a "soaking" dose of Ready Seal stain and go relax.

[plainpainter 217]

I'm sorry Pamela, disregard my previous post. Do exactly what you did last time except don't bother brightening - save yourself some hassle. Add a little TSP to your mix, rinse well. Then wait to dry and stain.

[RPetry 564]

I'm sorry Pamela, disregard my previous post. Do exactly what you did last time except don't bother brightening - save yourself some hassle. Add a little TSP to your mix, rinse well. Then wait to dry and stain.

Daniel,

Sage advice from a contractor that does not use Ready Seal. Or, from years of posts and pictures, work on a lot of Western Red Cedar.

It is not hard to learn more. What is hard is to unlearn when you discover yourself wrong. ~Martin H. Fischer

[plainpainter 217]

Rick - I've been working on western red cedar for over a decade longer than you have.

[Beth n Rod 1,279]

I agree with Rick, even if he's grumpy today. :cup:

Although Dan seems to be a tad grumpy too. Must be the rain.

Beth

[John Burdine 14]

So, lemme see if I'm tracking with Rick's advice. Under normal circumstances, Ready Seal doesn't need to be stripped, but since its 9 yrs old, its mostly faded any way and more than enough time for mildew to get in (and under?) the stain. Too risky to just bleach clean and recoat???

[RPetry 564]

So, lemme see if I'm tracking with Rick's advice. Under normal circumstances, Ready Seal doesn't need to be stripped, but since its 9 yrs old, its mostly faded any way and more than enough time for mildew to get in (and under?) the stain. Too risky to just bleach clean and recoat???

John,

No. Dependent on quality and age of the cut, cedar and also redwood tend to bleed tannin. A natural resin in the wood. It has to be removed prior to staining. Otherwise, the final finish will not appear consistent.

If Pamela had provided a few pictures, the diagnosis could be fine tuned.

NaOH in diluted mix works well. Of course, and acid is applied after cleaning. Its not Ready Seal as a stain, its the wood.

[plainpainter 217]

I agree with Rick, even if he's grumpy today. :cup:

Although Dan seems to be a tad grumpy too. Must be the rain.

Beth

Beth, I've been painting homes since around '90. I have never not seen a good TSP/Bleach mix not clean the wood and lighten up the wood. Bleach removes

tannins as well. And if you mix the TSP to bleach ratio just right - it's a one step cleaning process that both cleans and lightens. As well....as well, does a good

job at stripping the remainder of old finishes. Maybe not true with most woods, but a bleach/tsp clean leaves a much more natural looking wood finish than percarbs/NaOH/brightening

on cedar in my opinion. Oh yeah just to clarify - 95% of homes I have painted have been WRC clapboards or shakes.

[RPetry 564]

Beth, I've been painting homes since around '90. I have never not seen a good TSP/Bleach mix not clean the wood and lighten up the wood. Bleach removes tannins as well. And if you mix the TSP to bleach ratio just right - it's a one step cleaning process that both cleans and lightens. As well....as well, does a good job at stripping the remainder of old finishes. Maybe not true with most woods, but a bleach/tsp clean leaves a much more natural looking wood finish than percarbs/NaOH/brightening on cedar in my opinion. Oh yeah just to clarify - 95% of homes I have painted have been WRC clapboards or shakes.

Daniel,

I'm going to step on this, with your pardon.

As far as I know, most woodies on this board do not paint exterior wood. At least during the April - October wood season here in the Northeast U.S..

I've used acrylic paint on old growth WR cedar at my in-laws house down the Jersey Shore. Some basic painting prep, and it lasts a long time on vertical wood.

For the most part, for wood restoration, this web site is devoted to staining, not painting.

In my experience, NaClO does not emulsify cedar/redwood tannin, only "bleaches" it, changing the color. Sure you can remove some surface tannin build up by blasting the * out of the cedar, but that is by far not the best practice.

The purpose of NaOH (sodium hydroxide) is to emulsify the built up surface tannin. Low water pressure cleaning will remove the surface build up on the wood(s). You are not done yet.

Good cedars/redwoods still have a fair amount of tannin just below the surface substrate. That is why you never do a hard sanding on these woods. The heat of friction will drive those tannins back up to the surface, negating the work you started.

The next step is to suppress the tannin. That is where an acid wash comes into play. Not just to brighten/neutralize, but to get the natural wood tannin from leaching to the surface. With semi-transparent stains, such as Ready Seal, this step is critical.

[plainpainter 217]

The next step is to suppress the tannin. That is where an acid wash comes into play. Not just to brighten/neutralize, but to get the natural wood tannin from leaching to the surface. With semi-transparent stains, such as Ready Seal, this step is critical.

Please explain exactly how acid prevents future tannins from leaching to the surface?

[RPetry 564]

Please explain exactly how acid prevents future tannins from leaching to the surface?

Daniel,

The word "prevent" does not appear in any of my posts in this thread. The word I used was "suppress". There is a big difference in those two words.

From what I can understand, the cause of uneven, "blotched" semi-trans stain finishes on tannin rich woods such as cedars and redwoods is a bit more technical.

The stains from tannic acid are formed when iron and moisture come into contact with tannic acid in the wood. Oxalic and other acids reduce the iron compounds, therefore suppressing the formation of tannin staining.

Some good basic information can be found at http://en.wikipedia.org/wiki/Tannin

In part, as follows:

"Adding baking soda to the water to raise its pH level will accelerate the process of leaching, as the more alkaline solution can draw out tannic acid from the wood faster than the pH-neutral water."

One may speculate that a sodium hydroxide wood stripper would accelerate the process.

"Woods with a lot of yellow, red or brown coloration to them (like southern yellow pine, cedar, redwood, red oak, etc.) tend to contain a lot of tannin. Finnish hardwoods, like birch and aspen, do not contain tannins."

Edited September 26, 2011 by RPetry
additional information

[plainpainter 217]

I was always under the impression the stains formed when tannic acids of cedars, redwoods, & Fir come into contact with iron oxides is extremely localized around the fasteners - you are talking about staining that is more generalized. Other than these localized tannic/iron oxide stains, my impression is just the general increase in tannins caused by using caustic cleaners over the entire surface. When you use the correct fasteners for these woods, this isn't even an issue.

[RPetry 564]

Daniel,

Either you do not read what has been written, take the time to click and follow links, or just choose to be contrary with no basis in fact.

Water, the stuff out of the tap or well, has a fair amount of iron in it. Whether soluble or insoluble, irons are prevalent in nearly all water supplies. Don't worry, it will not harm you. In fact, your own chemistry and health depend on a fair amount of iron. If you do not drink normal water, eat a lot of calve's liver. In my experience, properly prepared, it is delicious.

This has nothing to do with sub standard fasteners. It has to do with the natural wood and water supply.