A clean, uniform appearance for visible edge bonds

In modern façade glazing and large insulating glass units, the edge bond can become a visible part of the overall design. When the glass edge remains exposed, even small irregularities in the butyl line can influence the appearance of the finished unit.

SP37 addresses this challenge with an extended black polypropylene cover integrated directly into the side walls of the spacer. It is designed to conceal visible irregularities in the butyl line and create a cleaner, more uniform appearance at the glass edge.

The challenge

The edge bond of an insulating glass unit has an important technical function. But in applications where the glass edge is visible, its appearance also matters.

Butyl application is not always perfectly uniform. Small waves or irregularities can remain visible through the glass and become part of the overall appearance of the façade or glazing.

This is particularly relevant for large glass units and façade applications, where architects, façade designers, and building owners increasingly pay attention to details that remain visible in the finished building.

The solution

SP37 is based on the rigid warm edge spacer SP18 and features an extended black polypropylene cover coextruded directly onto the vertical sides wall of the spacer.

The height of the black cover is designed to mask irregularities in the butyl line while leaving the necessary steel surface available for butyl adhesion.

The black layer is not painted, printed, or applied to the finished spacer afterwards. Instead, it is integrated directly into the profile during the production process, so no removal is possible during spacer transformation.

Key features include:

• Black polypropylene cover coextruded directly onto the spacer side walls
• Designed to mask visible irregularities in the butyl line
• No post-applied paint, print or ink
• Steel bonding area remains available for butyl adhesion
• Based on the rigid warm edge spacer SP18
• Developed particularly with visible edge-bond and façade applications in mind

Designed with processing in mind

The visual solution has been developed without losing sight of the requirements of insulating glass production. The integrated black side wall is part of the spacer design itself rather than an additional finishing step after profile production.

For insulating glass manufacturers, SP37 therefore brings together two aspects that are becoming increasingly important: reliable processing of a rigid warm edge spacer without any change in settings on standard bending machines set for Technoform spacers and a clean appearance in applications where the edge bond remains visible.

See the difference at glasstec

At glasstec 2026, visitors can see the effect directly in a comparative insulating glass unit. The exhibit uses deliberately irregular butyl application to demonstrate how the extended black side walls can reduce the visibility of these irregularities.

The comparison makes the principle behind SP37 immediately visible and shows why the appearance of the spacer can make a difference when the edge bond becomes part of the design.