Since the concrete is old and you may not know for sure if any type of oils grease and thin petroleum products have ever been spilled on the concrete we suggest degreasing the concrete regardless.
How to grind and stain concrete floors.
When rough grinding begin from one side and grind from west to east across the entire concrete floor.
If you have grease or oil on the floor you will need to use a degreaser or stain prep for concrete floors.
Learn how to prep your concrete for staining here.
If the floor still looks stained or patchy hire a floor grinder to grind away a thin layer from the surface of the concrete.
After several passes over the concrete floor with the 40 grit metal bond tool repeat the process with a finer 80 grit and 150 grit metal bond tool.
Be sure to overlap the grinding pass as close to the previous grinding pass as possible.
For example any filled in cracks or marks will likely stain.
Make sure you protect any doorframes and walls with painters tape.
Use a medium grade grinding head and apply it to the whole floor surface to ensure an even finish.
Before applying any stain you ll need to grind and ready the surface.
In this process the floor is cleaned using a minimum of two metal bond diamonds to cut the surface removing minor coatings and surface dirt.
It is also a longer term floor type when compared to topical polish.
This will remove the most stubborn remnants of most penetrating stains like oil and grease.
Concrete grinding staining and sealing is a great economical alternative to the full 10 step mechanical polish service.
Floors and counter tops created with concrete can be stained to any shade or color desired adding warmth to the space for relatively little money.