A good mix for brightening wood is two pounds of oxalic acid per 5 gallon pail. Even better is to mix your acids for better results. Most prepared brighteners use a combination of oxalic, phosphoric, and citric acids. The other acids are gentler on the human body and create different effects on certain woods. The best brightener I ever used on redwood was a blend, for example. I tried to find out the ratio for years, but it was a secret recipe from a manufacturer.
There are two secrets to making a good stripper: the amount of sodium hydroxide and the type of surfactants. Checking all of the available strippers today, you find a variation between a low of about 6% sodium hydroxide all the way to 75%. The surfactants are a huge part of that equation, too, with super-low sudsing being the most desirable.
Common wisdom in the industry is not to use any product stronger than you have to, so most manufacturers carry different strippers for different jobs. This is not a one-size-fits-all decision for most wood care professionals. Even the folks who use one brand of stripper often mix it hotter or cooler, depending on the job.
Mixing your own cleaners leaves you in a position of liability for your efforts. Contractors want consumers to hire a professional for cleaning because professionals do a better job. Contractors charge far less than the cost of a single DIY-consumer mistake. Cleaner manufacturers make the same plea to contractors: let the professional chemists come up with the best mix through knowledge and testing, carry the proper product liability insurance, etc.
As a contractor, your task is to find the best products at the lowest cost. I suggest that several manufacturers and distributors understand this, which is why they sell caustic strippers for as little as $1 per gallon (or even less). The savings (by making your own stripper-cleaner) might be a buck or two per deck. That amount of difference is not worth not having a $2M product liability policy alone.
Good luck in wood restoration. If we can help you in any other way, please call.
