What are the precautions for gluing puzzle boards?

Glue coating precautions  

White latex manufacturers recommend:  

1. Construction conditions  

The optimal bonding temperature for all-purpose adhesive is 25±5°C and a humidity of 55-75%. Stir thoroughly before use. Since all-purpose adhesive contains volatile solvents, maintain good ventilation during application and avoid exposure to open flames or high temperatures. Generally speaking, in winter, when temperatures drop below 5°C, all-purpose adhesive may gel, affecting its performance. Soaking the adhesive can in hot water at 30-50°C for 20 minutes will restore it to its original state, preserving its performance and allowing continued use.  

2. Surface requirements  

Before using all-purpose adhesive, it is essential to properly prepare the surface of the adherend, including degreasing, rust removal, moisture removal, and polishing to keep the surface clean, dry, and firm. Degreasing and cleaning can be done with a quick-drying solvent such as 120# gasoline, toluene, or ethyl acetate, and then allowed to dry. Polishing is generally done lightly with 0# or 1# sandpaper. Suitable for bonding plywood, flooring, bamboo, or other wood materials.

When applying glue, the moisture content of the adherend must be below 8% before applying glue. If it is higher than 8%, the adherend should be air-dried or baked before applying glue.  

3. Glue application  

Generally, one coat of glue is sufficient for the material. For porous materials, 2-3 coats of glue are required, and the next coat of glue can only be applied after the solvent of the previous coat has completely evaporated. Do not rush.  

To prevent air from entrapped in the adhesive layer, apply the adhesive in the same direction as the brush to facilitate air removal. However, be careful not to apply too quickly. Generally, a thinner adhesive layer results in fewer defects, less shrinkage, and higher bond strength. A thinner adhesive layer is preferable to a thicker one. Excessively thick adhesive layers can lead to defects such as poor drying, poor adhesion, and blistering. Therefore, while ensuring sufficient adhesive is not lacking, it's best to keep the adhesive layer as thin as possible. The ideal adhesive layer thickness should be between 0.08 and 0.15 mm, which translates to a glue dosage of 250 to 350 g/m².  

4. Let it air dry  

The purpose of air conditioning is to allow the solvent to evaporate completely, increase viscosity, and promote curing. After applying the adhesive, the solvent must evaporate completely. Do not bond immediately to prevent the adhesive layer from becoming sticky or creating bubbles, which can lead to a decrease in bond quality. The air conditioning time is generally 5-15 minutes at 25°C. Once the adhesive layer is dry (not sticky when touched with a finger), align and bond immediately. Do not allow the adhesive layer to dry out for too long, as this will cause the adhesive layer to lose its tack and affect bond strength.  

5. Bonding and pressing  

Universal adhesive has strong adhesion, so be sure to choose the right time when bonding. Do not move the adhesive back and forth. After bonding, press, hammer, or roll to remove air, compact the adhesive layer, and improve the bonding quality.  

6. Maximum strength  

Although all-purpose glue can form good adhesion in a short time, it takes 3-5 days to reach maximum strength. Therefore, joints with high bearing capacity should be left for a sufficient period of time before use.

7. Storage  

All-purpose adhesive should be stored in a cool, dry place away from children. Avoid direct sunlight. High temperatures, poor sealing, or prolonged exposure can cause the solvent to evaporate, resulting in excessive viscosity and making application impossible. Use toluene, ethyl acetate, butanone, or acetone to dilute the adhesive. Once the adhesive is thoroughly stirred, continue using.  

8. Others  

For furniture surfaces with wood grain or cat's eye paper, it's recommended to use water-based latex, as the strong solvents in all-purpose glue will otherwise dissolve the grain of the paper. All-purpose glue shouldn't adhere to plastics that are soluble in toluene, ethyl acetate, butanone, or acetone, such as rigid polystyrene foam (commonly known as styrene board). In these cases, it's recommended to use neoprene instead.