Vison Glass Block Mortar



Manufacturer: Vison Tech Products LLC


Product Description:

VISON Glass Block Mortar is a precise blend of Portland cement, lime, and aggregates mixed with other additives to provide a durable waterproof joint. Vison Glass Block Mortar is suitable for all glass-block masonry construction.



COLOR: White.

TEXTURE: Powder consisting of Portland cement, graded silica sand, organic and inorganic chemicals

PACKAGING: 50 lbs. Multi-wall bags.


Basic Use:

VISON Glass Block Mortar is used for laying glass blocks for both interior and exterior walls. The mortar can also be used for tuck-pointing, stucco, or other decorative applications where white mortar would be appropriate. Glass Block Mortar consists of a uniformly blended mixture of white sand, cement, lime, and chemical additives designed to provide a decorative, waterproof joint.


Key Benefits and Features

Vison Glass Block Mortar is resistant to mold growth. It can be used for tuck pointing and is ideal for new glass block interior or exterior applications.



This product is not recommended for surfaces prone to flexing, vibration, or movement. Do not apply over weak or unsound surfaces. Not recommended as a wear surface. For product installations, the temperature of the area to be leveled must remain above 50°F (10°C) for 72 hours. Under extreme weather conditions, appropriate cold weather to prevent mortar from freezing for the first 72 hours and elevated/hot-weather damp mist will be necessary to prevent rapid water drying out.


Applicable Standards

VISON Glass Block Mortar meets ASTM C 144, C150, C207 and exceeds ASTM 270 property requirements for Type “S” Mortar


General Surface Prep

All framing, pocket recesses, and chases must be accurately positioned and clean. Glass block must also be properly cleaned for the best bond. Follow the instructions of the glass block manufacturer for the best cleaning method. Coordinate the placement of corrosion-resistant anchors and glass block reinforcing bars and mark their positions. Expansion strips placed at the head and jambs should be held in place with a construction adhesive (reference glass block manufacturer’s recommendation for appropriate polyurethane construction adhesive). Allow expansion strip and adhesive to dry before block installation


Expansion Joints

Install expansion joints around all perimeters or restraining surfaces where possible to allow for expansion movement. Expansion joints shall be installed in accordance with local building codes.




For best results, maintain all materials, substrates, and work areas at 50°-70°F (10-21°C) for 24 hours before and 72 hours after installation. In a clean container, add 50 lbs. (22.68 kg) VISON GLASS BLOCK MORTAR to 4–5 quarts (3.8–4.7 L) of clean, cool water. Blend VISON GLASS BLOCK thoroughly for about 5 minutes. Stir material occasionally to keep the mix workable; however, no additional water should be added. Vison M4 Latex Admixture liquid, diluted 1:1 with water, may be added in the place of water to ensure better water resistance, a stronger bond, improved curing, and less shrinkage.  Do not over-water mortar. (A stiffer than mortar-like consistency is recommended as glass block will not absorb water like a typical CMU). Do not re-temper the mortar.



Prepare sill per glass block manufacturer's specifications. Place a full bed of freshly mixed mortar onto the base or sill. Set the first course of glass blocks into the mortar. Adjust the blocks with a level to ensure straight lines upon completion. Tap blocks into place with a rubber mallet. Do not place VISON Glass Block Mortar between glass blocks and expansion strips. Use a trowel to create recessed joints as work progresses. Follow the instructions of the glass block manufacturer for the proper placement of anchors and spacers. With the proper use of spacers, it will be much easier to keep blocks level and ensure a more professional finished wall. Reinforcing bars and panel anchors should be spaced every 24" (610 mm) vertically between glass blocks. The panel anchors are fastened through the expansion strip and into the jamb. Bend panel anchors horizontally into the joint and place reinforcing bars continuously from one side to the other. Apply half-width of mortar into the joint and position reinforcing bars into the mortar. Apply additional mortar and lay the next course. Maintain a uniform joint width of 1/4 - 3/4 inch. Use only wooden or rubber-tipped tools when tapping glass blocks in place. Do not realign, tap or move block after initial placement. Set succeeding courses of glass block. Space at the head of the panel and jambs must remain free of mortar for caulking. Do not bridge expansion joints with panel reinforcing. Tool, rake or finish joints before mortar reaches a final set. Refer to the glass block manufacturer's specifications for recommended installation instructions.



Per 50 lbs. (22.7 kg) bag will lay approximately:

36 - 6 inch block with 3/8 inch joint.

32 - 8 inch block with 3/8 inch joint.

18 - 12 inch block with 3/8 inch joint.

0.42 ft.3/50 lbs.


Working Time

Approximately 2 hours, depending on ambient temperature.



Clean tools, hands, and excess materials from the face of the tile, while the mortar is still fresh, with warm soapy water.  Use a damp cloth to remove all excess mortar from the surface of glass blocks before the mortar hardens. Polish off the remaining mortar residue with a clean, dry, soft cloth. Remove surplus mortar from the faces of the glass block at the time joints are struck or tooled. Mortar should be removed while it is still plastic using a clean, wet sponge or an ordinary household scrub brush with stiff bristles. Never use a wire brush to remove mortar from glass block surfaces. To remove the dry powder or stains from the glass surfaces, use a clean, dry, soft cloth or stiff nylon scrub pad.


Curing and Grouting

Cold temperatures or high humidity may extend curing time. Curing of masonry mortars is required only if conditions are very hot, dry, or windy. In such cases, a gentle fine mist of water applied to the surface will prevent premature drying and improve the strength of the mortar. Protect from direct sunlight, wind, rain, and frost during the curing period.