All I can say is what I use and what experience Ive had. I worked for my dad's masonry co. since 1987 and in those years we laid and yes cleaned many thousands of brick. Guess what.....we use d600 and wouldn't use anything else. Since then I have several more masons that keep me busy, I do clean other things..decks, houses, vehicles but I have cleaned more brick than anything else. There are always going to be people saying muriatic acid is too harsh or d600 isn't strong enough but that is My Method. I use d600 and like my results. I make very good money cleaning brick. I get 25 cents a square foot and can clean a brick front of a house by myself from the ground in 3 hrs on most days. I pocket 300.00 after my d600, fuel and whatever else so hey it works for me. If you want more profit go for it but I make out fine 2 of those a day in close proximity and Im very happy. I would hate to see brick that I had to clean that d600 wouldn't remove the mortar stains. Never said I didn't scrape the walls first. The tags (balls of mortar on the wall) must be removed mechanically first.I have a flat, steel scraper I rigged on a 20' extension pole. I can knock off most tags from the ground quickly. I then wet the wall very well, apply my d600 at whatever ratio I fell necessary to complete the job, let it dwell a few mins while scraping more if need be then reapply d600 again. Then I low pressure rinse (1500 - 2000 psi most of the time) very very well with 15 degree tip and vary the distance from the wall depending upon how stained it is. If you get the tags off all you have to remove are the stains, no problem for d600. I don't try to knock off a 3" x 3" mortar ball with acid and a powerwasher- not going to happen, but the stain will come off fairly easy if you can wash 2 weeks after the masons are finished. If it has been long it will be more difficult. Just because a lot of you use muriatic acid all the time doesn't mean you are right and I am wrong. I will stay with my tried and true methods. I pay 350 for 55 gallons of d600 and it can be cut 3 to 1 then downstreamed. I find this quite economical and profitable. Sorry for the long post but don't call me naive or unprofessional. My methods work for me, my masons are happy and my phone rings so I must be doing something right.
Mike