I would approach this crack the following ways
1. First purchase some dental tools from the local Army Surplus Store. Or if you know a dentist ask them for their old tools what you are looking for is the professional dental pic
2. Use the dental tool and acetone clean out the crack this should eliminate the dark area in the crack.
The dental pic will not open the crack any larger than it currently is.
3. Use a Polyester fill Clear if possible and the crack will be filled and you will hardly notice it.
What making the crack noticeable is the dirt that down in the crack remove the dirt fill the crack.
If the clear is not of your choice then mix a color to best match the stone.
I always tell my customer that a crack is a crack and the customer will always know where the crack is but the average person coming into the home would not notice it.
Hope this helps
John E. Freitag
The Stone and Tile School
I just looked at a floor of travertine tile. It has very
thin cracks (hairline)a few feet long in 3 different areas. How are
these cracks repaired? The travertine is light in color and the thin
cracks are dark.
This happened to me using VMC Kleerseal a long time ago, when flouro polymer technology was new and this was one of the first of these type sealer, water based. Don’t know why it happened but it was very noticable.
last year I used a water based sealer witch our customer spec out for us.We sprayed the sealer on limestone and it caused very light etching.We had only just began when we caught it so it was easy to correct.When I read the back of the bottle the instructions
mentioned some stones can be etched by using this product.Showed that to the customer and got the ok to use a product that we knew.
Anyway just heard a story that it happened to someone else only with a different water based sealer. I think siloxanes are corrosive (high alkaline) when not diluted.
I know that diluted in a sealer they are in small amounts so its not normal
for this to occur. Does anyone know why it does occur. Has anyone else had
this happen to them?