Fieldstone Patio Cleaning/Restoration

[nagurdj]

Pa. Fieldstone over concrete slab - has accumulated 22 years of mold/dirt/grease etc. Fieldstone has been sealed with whatever was on-sale that year at HD (e.g. Thompson's, Behr). Patio looks black in spots, white in others, and a few shades of green. Pressure washing (small household unit) only makes swirl designs. Grout will need replacing - BUT only if the fieldstone can be restored. Any ideas on cleaning - Muriatic acid? Any advice?

[Davestone]

Typically a pressure washer type soap like Krud kutter,and maybe a nylon scrub brush or buffer with nylon brush would work.And i'd say the old sealer is gone,try a real stone sealer next time.