I think you’ll be just fine on this project. Take plenty of before pictures because this will turn out nice when done. I would avoid any bleach on the limestone. Start with just plain water initially. I’d start around 1k-1.2k pressure. If you’re still left with staining, check out Sure Klean 942. Works really well for non polished stone.
Like you said, the fireplace is easy peasy.
Upsell sealing for sure on this. Siloxane PD or Natural Stone Treatment.
Living in Kentucky this state is full of limestone. I’ve been on many jobs people have called and said their rock or laid limestone has turned colors sometime after having it cleaned, what should I do. If I do use SH I have acid on hand to apply after using SH. Just personal preference, SH isn’t the cure all fo all surfaces. Most limestone I clean are on million dollar plus homes. Not throwing bleach on that. OneRestore works good too on limestone, Prosoco has several lines of chems too. I charge accordingly and explain to the customer, don’t really have an issue with it, they understand. I just sell our services and great chemicals help that.
I avoid SH on limestone because being so porous, limestone absorbs the SH and eventually crystallizes within the stone. This can cause future discoloration and/or complete degradation of the stone that would often be confused or misdiagnosed in the future when repairs are needed again. I opt for specialty chems and educate my customers why I use them. It costs more, sure, but peace of mind and longevity of service life is a ‘value’ to customers over ‘savings’.
Not saying it sounds negative, but would rather use chemicals made to clean and restore limestone. Considering they have a million dollar plus home , I want to give the homeowner quality chems and no chance of destroying their property. I’ve seen it first hand, believe me. These homeowners don’t bring their Mercedes to Walmart for oil changes they pay 4 times the amount at their dealership, there’s a reason why. Just educate the customer, not a problem, they get it, their used to it.
Do as mentioned above… hit it with 3-6% max (no surfactants), surface clean, rinse & repeat if need be…It’s important to mist the stone before applying the detergent, don’t soak it… Always, always…rinse out the detergent.
After talking things over with the customer there is now some question if it’s actually limestone at all. The ‘stone’ does have saw marks but unlike the 100 year old front porch where you can see little shells in the rock, this stuff is perfectly uniform with zero ‘naturalness’ to it.
I did try a 50/50 mix and 10 minute dwell on one square, turned it a tan color but still blotchy.