How to restore cracked marble surface

A Guide by Experts to Fix Cracked Marble Surfaces.
Marble surfaces or areas can develop different types of cracks that will include but are not limited to: from an impact, (something has been dropped on), inappropriately/poorly put in place, continually expanding/contracting (expanding/contracting) the surface material itself (due to heat variations), the building having settled down or there being a concentration of weight/stress on one specific area of the marble surface.
The important thing in determining why a crack has developed is how it can potentially cause additional damages. All marble is formed from natural processes occurring (metamorphic) using the calcite mineral which has transformed through crystallisation creating solid masses (a solid mass of marble). Although marble is far more sturdy than granite, marble does not have the same level of solidity (a softer material) along with a much greater level of porosity than granite.
The “category” of the crack type will also inform you of an appropriate repair method to use for that crack. There are three general categories of cracks, which are outlined below:
1. Hairline Cracks: Very thin, shallow cracks that exist only in the uppermost layer of the surface. There is no physical separation between them; thus they primarily represent cosmetic damage. Structural Cracking – Structural cracks generally have more separation between the two surfaces’ edges than a hairline crack, and/or there is some degree of height separation between the two surfaces’ edges; in addition, a Structural Crack may penetrate all the way through the thickness of a marble slab.

2. Corners and Edges Breaking Cracks – These types of cracks are caused by a sudden blow to an edge or corner of a marble slab, or due to a missing piece (chip) from an edge. The best way to repair a cracked marble countertop or tile is with epoxy adhesives which provide a strong, permanent bond between marble.

Step 2 – Prepare the Surface for Repair – The quality of your surface preparation greatly affects your repaired marble.

Prior to commencing repair work, do the following to clean the marble surface.

1. Remove any dust and debris from the marble surface using a soft feather duster.
2. Clean any oils or moisture from the marble surface with acetone.
4. Once you have cleaned the surface, allow the surface to fully dry prior to moving on to step 4.

**Water-based cleaners should never be used prior to applying the epoxy because of moisture retention resulting in a weaker bond.**

Step 3 – Selecting a Material for Marble Repair – Professional restoration firms generally use one of three types of materials to repair marbles:3 Types of Epoxy for Filled Cracks:
1. Horizontal/Edge/Vertical Knife-grade Epoxy
– Strongest structural bond; suitable for all surface types.
2. Low viscosity epoxy
– Gravity has an effect on it; fills hairline cracks, stabilizes surface.
3. Polyester Marble Filler
– Cures quickly; only for cosmetic repairs; not durable as epoxy.

The greatest option for an epoxy to create permanent repairs on natural marble is two-part epoxy.

Step 4: Fill the Crack

Fill in hairline cracks by:
– Injecting the flowing epoxy using a syringe or small applicator; capillary action will help draw the adhesive into the hairline crack.
– Using a straight-edge razor to remove any extra material before hardening.

Fill larger cracks by:
– Mixing the two-part epoxy according to packaging directions; if needed, add powdered marble pigments to the mixed epoxy to match existing marble colour.
– Applying the adhesive with a putty knife; slightly overfilling the area to allow for the slight shrinkage caused by the curing process; if doing it, then, make small batches so it won’t cure too soon.

The curing time for the epoxy/filler will depend on what type of adhesive you use. Fast curing epoxy typically cures in 20-60 min., whereas standard epoxy adhesive will take 24 hours to cure. Conversely, polyester fillers usually will cure in 15-30 min.Until your adhesive has cured fully, do not touch or polish the reconstructed area of the marble, because that could weaken the bond between the two materials being glued.
3. Sand the surface of the adhesive and restoratively finished area down to the level of the existing surface using 400 grit sandpaper. After the area has been levelled, use 800-grit, 1500-grit, and 3000-grit sandpaper to transition the restored area into the adjoining marble surface using a localized sanding method so that the surrounding marble does not become dulled by the effort of finishing the transition material. Professional restorers often use wet polishing pads and variable speed polishing machines to produce a smooth finish.
4. If you wish to restore the lustre to the marbled section of the restoration, you can use polishing powder (of a type specifically made for marble) combined with a felt pad or other soft polishing pad to buff the restoration area to have an equivalent mirror surface to the adjoining marbled surface. You may need to also use a final polishing compound to achieve an ultra-high lustre finish.
5. After you have completed your restoration, apply a penetrating sealer made for marble to help reduce the amount of moisture that can penetrate the surface of the marble, to reduce the risk of staining, and to extend the life of the repair. Cure the penetrating sealer as recommended by the manufacturer before returning to normal use of your marbled area.Improper cleaning of all surfaces can result in:

1) Not allowing enough time for curing
2) Over sanding around the marble surface
3) Not finding and repairing any structural problems under the surface.

Using good materials will help to get the best results and the longest lasting repairs, as well as keep the marble surface beautiful and durable.

Seek A Licensed Professional For Your Marble Repair If Any Of This Applies To You:

1) You have a crack through the entire slab
2) Your marble slab is part of a structure
3) Several/lots of slabs are loose/un-stable or if your marble is very expensive/high value/historic

In those cases you will probably need to reinforce the slabs with rebar or rods, and/or your slabs will most likely need to be removed and replaced.

Can I Repair My Cracked Marble?

Yes! If you can find a good epoxy adhesive, find an epoxy that is the same color as the two pieces to be taped together, and correctly sand and polish your repaired area to match the finish of the other adjacent pieces, your repair will be virtually undetectable! In most cases a properly prepared and stable foundation will provide a stable base for the marble.

If your foundation is unstable and the marble continues to move there is a good chance that the cracks will return.

Final Thoughts:

For complete restoration of cracked marble requires the correct evaluation of the cracks, the proper cleaning and preparation of the surface, the correct use of a Professionally made Epoxy adhesive, the careful sanding and polishing of the repaired area, the proper sealing of the area once repaired, and the proper care of the repaired area. If these steps are correctly performed, it is likely that the repairs will last for many years and that both the beauty and durability of your marble surfaces will be maintained.