ISL Therm-A-Glaze 60 Glazing Kit – 25 × 4mm is a complete dry intumescent glazing system developed for approved glazed apertures in 60-minute timber fire doors.
The system combines two complementary components:
During normal conditions, the components provide a clean and dry glazing arrangement without relying on wet glazing compounds. When exposed to fire conditions, the intumescent materials expand to protect the aperture, glazing beads and glass perimeter.
Therm-A-Glaze 60 was developed specifically to address the demanding conditions found around glass in 60-minute timber fire doors.
Uninsulated fire-resistant glass can become extremely hot during a fire. This may expose the timber door leaf and glazing beads to severe radiant heat and erosion.
The two-part Therm-A-Glaze system helps manage this by:
The product does not independently give a door or glazed aperture a 60-minute rating. Performance belongs to the complete tested or assessed glazing assembly.
Therm-A-Glaze 60 is designed as a dry glazing system.
This means the primary glazing components are supplied as preformed intumescent liners and seals rather than wet-applied glazing compounds.
Benefits of the dry system include:
The self-adhesive backing assists installation but does not replace the mechanical fixings required to retain the glazing beads and glass.
The visible 25 × 4mm component is Therm-A-Bead.
It consists of a moderate-expansion phosphate-based intumescent material contained within a PVC sleeve. The sleeve provides a neat visible finish beside the glass and is available in the stocked colours:
When activated by heat, the intumescent material expands and partially covers the timber beads, helping protect them from radiant heat and fire erosion.
Therm-A-Line is fitted around the perimeter of the prepared aperture beneath the glazing beads and glass arrangement.
The standard published kit arrangement uses:
Therm-A-Line is specially formulated to provide erosion resistance in a 60-minute fire-glazing construction.
The exact liner width must suit the door thickness, glazing beads and glass specified by the supporting evidence. Alternative Therm-A-Line widths should not be substituted without approval.
Therm-A-Glaze 60 is intended for suitable glazed openings in timber fire doors, used with approved fire-resistant glass and timber glazing beads.
Before installing the kit, confirm that the door evidence permits:
Machining a glazed opening into a certified fire door without suitable evidence can invalidate its certification and fire-performance claim.
The manufacturer’s published basic arrangement includes:
This is a published reference arrangement rather than a universal installation detail. The current doorset evidence takes precedence.
The stocked colour options apply to the PVC sleeve surrounding the Therm-A-Bead component:
The manufacturer’s wider range also references Cream and Red, but these finishes are not included within the current selectable stock range.
Before ordering, confirm:
| Product Name | ISL Therm-A-Glaze 60 Glazing Kit – 25 × 4mm |
| Manufacturer | Intumescent Seals Ltd |
| Product Range | Therm-A-Glaze 60 |
| Product Type | Two-component dry intumescent fire-glazing system |
| Application | Approved glazed apertures in timber fire doors and supported glazed screens |
| Published Fire Performance | Up to 60 minutes as part of an approved complete glazing assembly |
| Therm-A-Bead Size | 25 × 4mm |
| Therm-A-Bead Length | 2100mm |
| Therm-A-Bead Material | Moderate-expansion phosphate-based intumescent contained within a PVC sleeve |
| Standard Therm-A-Line Size | 54 × 2 × 2100mm |
| Therm-A-Line Function | Erosion-resistant intumescent aperture liner |
| Fixing | Self-adhesive positioning with mechanically fixed glazing beads |
| Stocked Colours | Black, Brown and White |
| Test Standard | BS 476 Parts 20 and 22 |
| Certification Reference | Certifire CF284; confirm current certificate validity and scope before reliance |
| Standalone Fire Rating? | No — the rating applies to the complete tested or assessed glazing assembly |
| Standalone Smoke Rating? | No separate cold-smoke classification should be assumed |
| Standalone Acoustic Rating? | No |
| Colour | Therm-A-Bead Size | Component Length | Product Code |
|---|---|---|---|
| Black | 25 × 4mm | 2100mm | THE60/BLK |
| Brown | 25 × 4mm | 2100mm | THE60/BRN |
| White | 25 × 4mm | 2100mm | THE60/WHT |
| Size Options | Colour Options | Total Variations |
|---|---|---|
| 25 × 4mm Therm-A-Bead | Black, Brown and White | 3 |
The applicable doorset evidence must be checked before adopting these dimensions.
The manufacturer and current supplier pages continue to reference Certifire CF284.
However, the publicly linked certificate available during this product review was reissued in March 2020 and states a validity date ending on 8 March 2025.
Before specifying the system for a current certified project, obtain confirmation of:
Therm-A-Glaze 60 must be installed as part of an approved fire-resistant glazing assembly.
Before beginning work, confirm that the door, aperture, glass, glazing beads, setting blocks, liner and fixings match the applicable test evidence or doorset assessment.
Machine the glazed opening only where permitted by the doorset evidence.
Install the specified hardwood aperture liner around the complete opening. The manufacturer’s basic published arrangement uses a 16mm hardwood liner with a minimum density of 650kg/m³.
The liner should be securely fitted with closely formed corner joints and no unsupported sections.
Measure and cut the Therm-A-Line liner to fit around the aperture perimeter.
Apply it continuously to the location specified by the glazing-system evidence, using its self-adhesive backing for positioning.
Ensure that:
Prepare the hardwood glazing beads to the dimensions required by the approved system.
The published basic arrangement uses beads approximately 30 × 25mm, including a 5 × 5mm bolection return and an approximately 20-degree chamfer.
Clean the surfaces receiving the Therm-A-Bead seals.
Apply the 25 × 4mm Therm-A-Bead seal to each glazing bead using its self-adhesive backing.
Position the seal so that it will sit correctly between the bead and glass when the assembly is completed.
Cut all sections cleanly and keep joints closely fitted. Do not stretch the profile or leave gaps at the bead corners.
Position and mechanically secure the first set of glazing beads.
The manufacturer’s published basic arrangement uses No. 8 screws, 50mm long, installed at maximum 150mm centres.
Use the exact fixing arrangement stated by the current doorset evidence.
Fit the specified non-combustible or hardwood setting blocks.
Carefully position the approved fire-resistant glass so that:
Install the opposing bead assembly with Therm-A-Bead fitted in the same approved position.
Tighten the mechanical fixings progressively while checking that the glass remains correctly centred and is not subjected to excessive local pressure.
Check the completed glazing system on both faces.
Therm-A-Glaze 60 does not independently provide a 60-minute fire rating.
Performance depends on the complete assembly, including the timber door construction, aperture, glass, hardwood liner, Therm-A-Line, Therm-A-Bead, glazing beads, setting blocks, mechanical fixings and installation quality.
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