Jon,
Read your post about mixing oxalic acid and citric acid together and using one pound per gallon of water.
Both of these products will do the same thing, why are you mixing them? Oxalic is a stronger acid therefore it will react quicker than citric. This is the main reason that we use it. We are able to see the reaction quicker so we don't use as much product. We tried using citric but found that we were using four times more product because we could not tell where we applied at and just keep going over the same areas. Oxalic, you spray, you see, you keep going. Although citric is slower reaction, it is safer to use.
As for your mixture. One pound per gallon of water is way to much. The molecules of water will only absorb so much acid. Once the molecules are saturated, they will not accept any more. You must be getting a lot of undissolved crystals in the bottom of the pail. If your not, then you are spraying these crystals directly onto the wood substrate. If your sucking up these undissolved crystals, you are probably having problems with your sprayer clogging up to. In short, you should be able to get the same results by adding one and one have pounds of oxalic to five gallons of water. If you have hot water, the crystals will dissolve better.
Someone asked if you could put to much oxalic/citric on a wood substrate, yes you can. In most cases, it would just mean a lot of rinsing to remove it. In some cases if you don't get it all off, it will re-appear in a white powerish form on top of your finish. It can also cause a chemical reaction with your finish and cause premature failure. There is another condition that can occur if you apply to much but it is to complex to go into at this time.
I have seen a lot of you are having troubles with the fuzzies. Wood is going to fuzz up to some degree when you pressure wash. Just how much will depend on several factors. One being on how much exposure the substrate gets and how it's been protected. Keep in mind that although the finish may look good, it does not mean that it is protecting the wood. Fences and railing get the most exposure therefore tend to fuzz up more. Another factor that causes the fuzzies as you call it, is the use of bleach in prior cleaning. I know that a lot of you use bleach and I don't want to get into a debate over it. Bosie Cascade is the largest user of bleach in the world. They use it to break down the wood fibers in their wood pulp plants. Wood fibers = fuzzies.
As you can see, sometimes I just don't know when to shut up. Talk to you all later.
Jim Bilyeu
Exterior Woodcare
