Superior Hardener

Superior Stone Products Hardener – Precision-Formulated Curing Agents for Stone Fabrication Adhesives

Superior Stone Products Hardeners are engineered curing agents designed specifically for use with Superior's line of stone fabrication adhesives. Available in two formulations — BPO (Benzoyl Peroxide) white paste and MEKP (Methyl Ethyl Ketone Peroxide) clear liquid — these hardeners are matched to their compatible adhesive systems to ensure consistent, reliable cure performance on the job site. Each adhesive sold by Superior Stone Products is packaged with the correct amount of hardener to maintain optimal mixing ratios out of the box. These products are intended for professional contractors and fabricators working with natural stone, engineered stone, and related materials.

Unlike generic or off-brand hardeners, Superior's hardeners are precisely calibrated to their companion adhesive formulations, eliminating guesswork and reducing the risk of bond failure caused by incorrect ratios. Using the matched hardener ensures proper open time, full cure strength, and color consistency — variables that generic substitutes cannot guarantee. Substituting incompatible hardeners or altering the ratio without manufacturer guidance risks compromising the structural and aesthetic integrity of the finished installation.

Key Features & Benefits

Two Hardener Types for Specific Adhesive Systems

The BPO white paste hardener is formulated for use with polyester, vinyl ester, and acrylic adhesives, while the MEKP clear liquid hardener is designed exclusively for polyester water-clear adhesives. Having the correct hardener type matched to your adhesive system is critical — using the wrong type can result in incomplete curing or bond failure. Superior takes the guesswork out by packaging the right hardener with each adhesive product.

Pre-Measured with Every Adhesive Purchase

Superior Stone Products adhesives are sold with the correct amount of hardener included, ensuring proper mixing ratios without requiring contractors to source or measure hardener separately. This eliminates a common source of error on busy job sites and helps maintain consistent results across multiple installations. Contractors can trust that every tube or cartridge contains the exact hardener quantity needed for that adhesive formulation.

Optimized Mixing Ratio Compliance

Following the mixing ratio specified on the adhesive product label is essential to achieving full bond strength, correct working time, and color stability. Over-hardening is a frequent field error that causes brittleness, reduced bond strength, and discoloration — even at lower temperatures. Superior's system is designed so that using only the included hardener quantity naturally keeps users within the correct ratio.

Prevents Common Adhesive Failures

Too much hardener causes the cured adhesive to become brittle, weakens bond strength, and can cause visible discoloration in the finished joint — problems that are costly to remediate after installation. By providing hardener in pre-measured quantities and publishing clear usage guidelines, Superior helps fabricators avoid these failures before they occur. Adhering to the label instructions is the single most important step in preventing hardener-related adhesive defects.

Compatible with Recommended Mixing Practice

Superior recommends using a disposable paper cup as the mixing container for adhesive and hardener, as it does not absorb resin or introduce contamination. Scrap cardboard should be avoided because it absorbs resin and hardener, throwing off the mix ratio; scrap stone should also be avoided as it can cause premature curing or contamination of the mixed adhesive. Using the right mixing vessel is a simple step that protects the integrity of the cure.

Manufacturer-Specified Formulation Integrity

Superior explicitly advises against substituting other hardeners or modifying the ratio unless specifically directed by the manufacturer. This ensures that fabricators are always working within tested and validated parameters for the specific adhesive they are using. When in doubt, consulting Superior Stone Products directly ensures compliance with the system's design intent.

Common Applications

Countertop Seaming and Repair

Used with Superior polyester, vinyl ester, or acrylic adhesives for seaming natural and engineered stone countertops, where bond strength and color match are critical to a professional finish.

Water-Clear Joint Work with MEKP

The MEKP clear liquid hardener is specifically used with polyester water-clear adhesives for applications where joint transparency is required, such as clear or light-colored stone installations.

Sink and Undermount Cutout Reinforcement

Used in conjunction with the appropriate Superior adhesive to reinforce sink cutouts and undermount installations, where a fully cured, high-strength bond is required.

Stone Crack and Chip Repair

Hardener is combined with compatible adhesives to repair cracks, chips, or voids in stone slabs and fabricated pieces, restoring structural integrity and appearance.

Edge Lamination and Build-Up

Applied with polyester or acrylic adhesives during edge lamination to bond stone strips and build up profiles, requiring consistent cure performance across multiple bonded layers.

General Stone Bonding Applications

Any application requiring Superior Stone Products adhesives — including backsplash installation, stone panel bonding, and decorative stone work — relies on the correct hardener to achieve proper adhesive performance.

Compatible Materials

• Natural stone (granite, marble, quartzite, travertine, limestone)
• Engineered stone / quartz surfaces
• Polyester adhesive systems
• Vinyl ester adhesive systems
• Acrylic adhesive systems
• Polyester water-clear adhesive systems (MEKP only)

Product Documents

• Superior HARDENERS Directions
• Cream Hardener – BPO (PDF)

Application Instructions

Step 1: Review the Adhesive Product Label

1. Locate the mixing ratio and hardener quantity specified on the adhesive product label.
2. Confirm that the hardener included with the adhesive matches the required type (BPO white paste or MEKP clear liquid).
3. Do not substitute a different hardener type or alter the specified ratio without guidance from Superior Stone Products.

Step 2: Prepare Your Mixing Container

1. Use a clean disposable paper cup as your mixing vessel.
2. Do not use scrap cardboard — it absorbs resin and hardener, causing off-ratio mixing.
3. Do not use scrap stone — it can cause premature curing or contamination of the adhesive.

Step 3: Mix Adhesive and Hardener

1. Dispense the adhesive into the disposable paper cup.
2. Add only the amount of hardener specified on the adhesive product label — do not add more.
3. Mix thoroughly according to the adhesive label instructions until a uniform consistency is achieved.

Step 4: Apply and Cure

1. Apply the mixed adhesive immediately per the adhesive product's open time specifications.
2. Allow full cure time as specified on the adhesive label before loading or finishing the joint.
3. Dispose of used mixing containers and any unused mixed adhesive according to local regulations.

Technical Specifications

Frequently Asked Questions

Q: Which hardener do I use with my Superior adhesive?
A: The correct hardener is included with each Superior Stone Products adhesive purchase. BPO white paste is used with polyester, vinyl ester, and acrylic adhesives; MEKP clear liquid is used exclusively with polyester water-clear adhesives. Always verify by checking the adhesive product label.

Q: Can I use more hardener to speed up cure time?
A: No. Using more hardener than specified on the adhesive label will make the adhesive brittle, weaken bond strength, and cause discoloration — even in cooler temperatures. Always use only the amount specified on the product label.

Q: Can I substitute a different brand of hardener with a Superior adhesive?
A: No. Do not substitute other hardeners or modify the ratio unless specifically directed by Superior Stone Products. Substitution can compromise the adhesive's performance, cure characteristics, and bond integrity.

Q: What mixing container should I use?
A: Use a disposable paper cup. Avoid scrap cardboard, which absorbs resin and hardener causing off-ratio mixing, and avoid scrap stone, which can cause premature curing or contamination.

Q: How do I know the correct mixing ratio?
A: The mixing ratio is specified on the adhesive product label. Because Superior adhesives are packaged with the correct amount of hardener, using the full included quantity with the full adhesive unit naturally achieves the correct ratio when following label instructions.

Q: What happens if I use MEKP with a non-water-clear polyester adhesive?
A: MEKP is formulated specifically for polyester water-clear adhesives. Using it with other adhesive types — such as polyesters, vinyl esters, or acrylics that require BPO — may result in improper curing, reduced bond strength, or adhesive failure. Always match the hardener type to the adhesive system as specified.