Bonstone Last Patch Limestone Patching Compound – Quart Kit

Bonstone Last Patch Limestone is a two-part patching compound for limestone and sandstone. It is used for aesthetic patches and repairs on coarse grained stones, concrete, and masonry substrates. Added colors and filler match the color and look of textured stone, and the cured patch absorbs water the way the porous stone around it does, so a repair weathers with the surrounding surface instead of standing out as a lighter or darker spot. Nine stock colors are available, and colors can be blended or tinted on site for a closer match.

Pick Your Color

Select the color from the dropdown above. If you are working from a Bonstone color card or a sample off a previous job, match the color name here.

The Bonstone color card also shows two blended shades: half Indiana Gray with half Texas Cream, and half Indiana Buff with half Texas Cream. Those are field mixes, not separate products. Buy both base colors and blend them on the job.

Watch: Last Patch Limestone

What Ships in the Quart Kit

• One quart of Part A in the color you select (thick, sand-like mortar)
• Four 1 oz tubes of Part B hardener (clear, watery)
• Measuring cup for the 7:1 mix

Key Product Details

Mixing at 7:1 by Weight

Bonstone gives two ways to hit the ratio without a scale. Mix only what you can place, and apply immediately.

Small batch

• Fill a cup to the 1 oz mark with Part A (about 49 grams)
• Fill a second cup to the 1 tsp mark with Part B (about 7 grams)
• Combine in a third container, mix thoroughly, use right away

Full tube batch

• Fill the provided cup with Part A four times, emptying each into the mix container (about 196 grams)
• Empty one entire 1 oz tube of Part B into the container
• Mix thoroughly and apply to the repair area immediately
• Add more Part A if needed to reach a mortar-like consistency

Working Notes

• Apply the material as flush to the stone surface as possible before dry grinding. Less overfill means less grinding time.
• Latex gloves help you form and shape the material around corners and edges.
• Up to 10 percent of your own stone dust can be added to the mix for texture and tone.
• Powdered tints adjust for variations in stone color when a stock color is close but not exact.
• Colors can be combined for a closer match on variegated stone. Test in an inconspicuous area first.
• Because the compound is UV stable, exterior patches on steps, sills, and pavers hold their color under sun exposure.
• For a faster set, add Bonstone Universal Accelerator. Not recommended for work above 85 degrees F.
• Wear gloves, a mask, and safety glasses. Review the SDS and TDS before use.

Common Applications

• Structural patching on limestone and sandstone
• Repairing broken corners, steps, and sills
• Patching chips, holes, and spalls
• Crack repair in limestone panels
• Patching exterior pavers
• Monument, sculpture, and facade restoration
• Patching on concrete and masonry substrates

Related Products

• Last Patch Limestone Repair Kit, the small kit with Buff, Gray, and Texas Cream plus tools and accelerator
• Bonstone Universal Accelerator, 0.5 oz and 2 oz bottles for faster set times
• Last Patch Powdered Tints, seven blendable pigments in 1 oz jars or a set of seven
• Bonstone Liquid Tints for tinting adjustments
• Bonstone Stone Granules for texture matching
• Historical Restoration Mortar (HRM) for restoration work where a softer, mortar-matched patch is specified
• All Bonstone stone repair products

Questions Fabricators Ask

What stone does Last Patch Limestone work on?

It is designed for limestone and sandstone, and it is used for aesthetic patches and repairs on coarse grained stones, concrete, and masonry substrates.

What is the mix ratio for Last Patch Limestone?

Seven parts Part A to one part Part B, by weight. Bonstone provides two cup-based methods so you do not need a scale on the job.

How long does it take to set?

About 45 minutes at 75 degrees F. Cooler conditions slow it down. Universal Accelerator speeds it up when the job is below 85 degrees F.

Can it be used in cold weather?

Yes. It can be used in below freezing temperatures. The surface still has to be dry.

What if none of the nine colors match my stone?

Two options. Blend two stock colors, which is how Bonstone builds the blended shades on its color card. Or adjust a stock color with Last Patch Powdered Tints and up to 10 percent of your own stone dust.

Last Patch Limestone or HRM?

Bonstone rates Last Patch Limestone as the stronger of the two. Reach for HRM when the spec calls for a restoration mortar matched to historic masonry. Reach for Last Patch Limestone when the patch needs strength, UV stability, and a color match to textured stone.

Should I buy the quart kit or the small repair kit?

Buy the quart kit when you know the color and have real volume to fill, like a run of step or sill repairs. Buy the Repair Kit for small service calls or when you want to try three common colors before committing to a quart.

How much surface does one quart kit cover?

Coverage depends on patch depth and how much you overfill for grinding. Call 800-220-1966 with your repair sizes and we will help you size the order.

Need a Color Match?

Send us a photo of the stone and we will point you to the closest starting color and tint. Call (800) 220-1966 or email [email protected].