Characteristics of natural glues

Casein Type adhesives

Applications	• tropical woods; • structural lamination, • panel and flush door covering; • may produce glue lines with a thick appearance.
Availability/ using	• requires careful two-step mixing with water.
Typical working time #	15 to 45 minutes
Clamp time #	2 to 8 hours
Cured working properties	• cures hard, sands readily, but dulls cutting tools rapidly; • permanently stains the surface of high-tannin woods such as oak and mahogany.
Cured properties	• excellent strength, rigidity and durability; • highly creep resistant; • some gap-filling ability.
Long-term properties	• high-grade formulas have good moisture and solvent resistance; • low-grade formulas have lower moisture resistance; • can be subject to bacterial and fungal attack unless preservative is added.

# depending on glue formula, moisture content of workpieces, working temperature, atmospheric humidity etc

Applications	• light-duty, wood-to-wood bonding; • natural nonwood materials (such as cloth, metal and bone) to wood.
Availability/ using	• ready to use; • can be coloured with dyes etc; • refrigerate to extend shelf life.
Typical working time #	15 to 30 minutes
Clamp time #	2 to 4 hours
Cured working properties	• cures hard; • machines and sands well; • compatible with stains and finishes; • reversible with water.
Cured properties	• good strength, rigidity and creep resistance; • not as strong as hide glue.
Long-term properties	• Excellent heat and solvent resistance; • poor water resistance; • glue layers desiccate with time and becomes brittle.

# depending on glue formula, moisture content of workpieces, working temperature, atmospheric humidity etc

Applications	• good combination of versatility, compatibility and strength; • edge- and face-gluing, assembling joints; veneering, repairing and bonding natural nonwood materials to wood. • also used for sizing, a wood conditioner and a grain filler.
Availability/ using	• granules -mix with water and heat to 140°F before use; • ready-to-use liquid hide glues also available; • add water if glue thickens; • add urea or salt to retard gel rate; • can be coloured with dyes etc.
Typical working time #	1 to 10 minutes
Clamp time #	10 to 90 minutes
Cured working properties	• Cures very hard; • machines and sands well.
Cured properties	• excellent strength, rigidity and creep resistance; • thick glue layers can be brittle.
Long-term properties	• resistant to moderate heat and moisture levels, despite reversibility; • good solvent resistance and shock resistance; • glue layers desiccate with time and becomes brittle.

# depending on glue formula, moisture content of workpieces, working temperature, atmospheric humidity etc

Applications	• bonding porous, pliant materials (such as paper, cloth and leather) to wood; • commercial formulas require no cooking and are easy to use.
Availability/ using	• mix with water and cook before use (if required); • add preservative to prevent mould growth; • can be coloured with dyes etc.
Typical working time #	15 to 20 minutes
Clamp time #	3 to 6 hours
Cured working properties	• Cures soft and flexible; • Easily cut with hand tools; • compatible with stains and finishes; • reversible with water.
Cured properties	• not strong enough for most structural wood-to-wood bonding.
Long-term properties	• subject to bacterial and fungal attack unless preservative is added.

# depending on glue formula, moisture content of workpieces, working temperature, atmospheric humidity etc