This is food for algae, mold and fungus.
Anybody that tells you that there is no need to rinse after a blast is taking a short cut. There are 2 reasons it should be rinsed. First reason is that you cannot remove any and all mold and fungus with blasting alone. You have to rinse the house with a mild bleach concentrate in order to kill any fungus, spores or mold that are in the small places blasting can’t get to. The second reason is that the dust from the blasting cannot be 100% removed by blowing it down with air. In addition, that dust that remains is what? Corn cob. This is food for algae, mold and fungus. Make sure you get a good job, not a cheap job!
You should get the house borated between blasting and staining. This is the only time it can be done as borate needs to be applied to bare wood and you have to let it dry. Again, time to do it right. Time to wet the house down, time to apply the borate. Time is money. This should be a part of your price. If it isn’t, ask up front how much to add it to the scope before signing the contract.
