To determine the open time of tile adhesive according to standard laboratory testing methods

1. Aim

To determine the open time of tile adhesive,
i.e. the maximum time after application during which tiles can be fixed with proper bonding.

2. Apparatus / Materials Required

• Tile adhesive sample
• Clean water
• Mixing tray / mixer
• Notched trowel (6 mm)
• Concrete / cement board substrate / Gypsum Board
• Ceramic tiles (50 mm × 50 mm recommended)
• Timer / stopwatch
• Weighing block
• Marker / chalk for marking time intervals

3. Method / ProcedureThe tile adhesive is first prepared by mixing it with clean water in the manufacturer’s recommended proportion until a uniform, lump-free paste is obtained. The mixture is allowed to rest for 5–10 minutes (slake time) and then remixed before use.
The adhesive is then applied evenly on a clean, dry cementitious substrate using a notched trowel held at approximately 45° angle to form uniform ribs. Immediately after application, a timer is started and tiles are placed on the adhesive bed at predetermined time intervals such as 5, 10, 15, 20, 25, 30, 35, 40 and 45 minutes.

At each interval, a tile is pressed firmly onto the adhesive and then removed after a short duration (around 30 seconds) to examine the adhesive transfer on the backside. This process is repeated for all time intervals, and the condition of adhesive coverage is observed carefully. The open time is determined as the maximum time interval at which proper adhesive transfer and bonding is still achieved without skin formation on the adhesive surface.

4. Observation Table

5. Result

The open time of the tile adhesive is determined based on adhesive transfer on the backside of a 50 mm × 50 mm tile piece.

At each time interval, the tile is removed and visually checked. The adhesive should cover minimum 50% of the tile backside surface.

• ✅ If adhesive coverage is ≥ 50% → Result is Pass (Within Open Time)
• ❌ If adhesive coverage is < 50% → Result is Fail (Open Time Exceeded)

Final Result:

Open Time of Adhesive = ______ minutes
(Last time interval at which ≥ 50% adhesive transfer is achieved)