It’s no wonder why Bluestone is such such a popular paving material. When selected and installed correctly, it looks amazing.
Unfortunately, one of the hidden problems with Bluestone is that there are ferrous minerals incorporated into the composition of the stone, which often turn into Rust Spots. These spots can most often be prevented using a few preventative measures.
Most importantly for installers and masons, NEVER use Muriatic Acid to clean cement and grout residue from the stone. Unfortunately, many masons learned that they can quickly and cheaply remove dried cement from stone and brick using Muriatic Acid which costs less than $10.00 per gallon, and it is a very caustic and effective cleaner of cement residue. However, like all acids, it is an oxidizer of metals. It is particularly harmful to Bluestone, as we have had many customers calling us with horror stories about damage.
In many types of natural stone, and Bluestone in particular, rust is inherent in the composition of the minerals. When exposed to moisture, and particularly when exposed to an oxidizer like Muriatic Acid, it accelerates the growth of rust and it begins to leach out onto the face of the stone. (see image below)
In some cases, the rust can be so severe that individual stones need to be removed and replaced. We always recommend the least aggressive cleaners, and progress, if needed to acids to minimize harming the stone, or changing the look of natural stone, particularly Bluestone. We suggest cleaning grout residue with a non-acid cleaner like HMK R155 Intensive Cleaner.
Secondly, and very important, is to protect all natural stone with a professional grade sealer. Solvent based impregnators work best and stop the acceleration of oxidants. Impregnators come in two types, Invisible and Color Enhancers. For exterior applications, and to get exceptional results I suggest HMK S31 Silane Impregnator. To obtain a deeper and richer color, I suggest using the HMK S42 Color Enhancer. For outdoor kitchen and food areas, for extra Stain Protection, particularly with oil stains, I suggest HMK S244 Color Enhancer Extra.
As a stone professional and contractor using and testing all the leading brands, HMK Stone Care System products (Germany) consistently provide superior results.
If you have a question or problem with your Bluestone, please email me and I will reply within one business day: firstname.lastname@example.org