Repairing granite countertop scratches requires caution, but it can save thousands of dollars compared to the cost of replacement. Scratches, scuffs, and unsightly abrasions can happen with normal use, even when people are being careful, so this is a fairly common problem.
One general note to remember: keeping a close eye on the buffing of a granite scratch is imperative. Even slight abrasions can quickly out of hand with too much force. To avoid ruining the countertop, work slowly and steadily.
Step 1 - Resin Scratch Stick
For small scratches, a resin scratch stick is the best place to start. It won't hurt the polish, but it should render the scratch invisible. Though the scratch will still be there, it won't be visible to the naked eye. Take the resin scratch stick and drag it across the mark in the countertop. The scratch should fill in and disappear. If this doesn't work well enough for your taste, proceed to step two.
Step 2 - Ultra Fine Steel Wool
If the scratch is so deep that the resin stick can't cover it up, ultra fine grit steel wool or sandpaper is a good option to try next. Slowly abrade the surface of the scratch with the steel wool. Begin lightly and increase the pressure gradually. It's much worse to take off too much than too little, so take it slow.
Work either side of the scratch to minimize the polish and then begin scouring across the scratch. Use small linear movements, not circles. In time the scratch will be scoured out and removed. Follow this process up by applying a rubbing compound and stone sealer to complete the finish. If you're still not happy with the outcome, move on to step three.
Step 3 - Diamond Sanding Block
Diamond sanding blocks are one step up from the abrasive qualities of sandpaper or steel wool. These tools feature fine-grit diamonds attached to paper and mounted on a sanding block, and allow you apply the hardness of diamonds to the granite surface. Proceed with caution. The diamonds will further scuff other areas which have not been damaged if you're not careful.
Move the sanding block along the sides of the scratch first and then begin crossing over the scratch to buff it out. Small motions back and forth should be sufficient. Rinse the surface clean of debris and dust (there should be plenty) and then apply the rubbing compound to buff out any uneven marks. Finish with the stone sealer to preserve the shine.
Step 4 - Call the Professionals
If these steps weren't enough to buff out your scratch, it is probably just too deep for home repairs. Rather than permanently damaging the valuable granite surface, swallow your pride and call some professionals for advice. Going forward, consider applying a granite sealant every other year to help prevent further scratches.