A label, not a chemistry
'Yellow glue', 'carpenter's glue' and 'PVA' are often used as if they meant the same thing, and they do not. Titebond describes Original as an aliphatic resin emulsion, Titebond II as a cross-linking polyvinyl acetate and Titebond III as an 'advanced proprietary polymer'; it calls Speed Set a PVA while listing its type as an aliphatic resin emulsion. The Wood Handbook groups the plain emulsions as poly(vinyl acetate), 'also known as white glue', and the cross-linking ones separately, because they resist moisture and heat better. Colour is no guide either: Titebond lists Original as drying yellow, II translucent yellow and III light brown. Read the maker's description of the product, not the bottle's colour or name.
The adhesive families
| Family | How it sets or cures | Gaps | Moisture | Typical use |
|---|---|---|---|---|
| PVA emulsion | Loses water at room temperature | Does not fill gaps well | Low resistance to moisture and heat | Furniture and general shop work, indoors |
| Cross-linking PVA | Like PVA, with copolymers that cross-link | Does not fill gaps well | Improved resistance to moisture and heat | Doors, millwork, work that may get damp |
| Polyurethane | Reacts with moisture on the surface and in the air | The Handbook lists it as gap-filling; Gorilla lists its own glue as not | Resistant; limited against prolonged, repeated wetting and drying | Mixed materials, damp conditions |
| Epoxy | Resin and hardener react; limited pot life | Gap-filling, and thickened with fillers | Resistant; delaminates with repeated wetting and drying | Repairs, gaps, wood to other materials |
| Cyanoacrylate | Sets in seconds; an activator speeds it | Thicker grades fill small voids | Softens slightly with water; interior use (Titebond) | Small parts, cracks, fixtures |
| Hide (animal) glue | Hot: sets on cooling and drying; liquid: sold ready to use | — | Not water resistant; moisture lets it be undone | Furniture repair, restoration |
Families and behaviour from the Wood Handbook's Table 10–1; the cyanoacrylate row and the liquid hide glue from Titebond, the polyurethane gap claim from Gorilla. Each row is a family: individual products differ.
- Gaps. The Wood Handbook says most wood adhesives do not fill gaps well, which is why fit matters more than glue. Epoxy is the family built to bridge them; polyurethane foams, but foam is not bond strength — Gorilla's own specifications say its glue expands three times yet list gap filling as 'no'.
- Creep. The Wood Handbook says PVA joints yield under continued stress — worth knowing for a joint under constant load. Titebond describes its liquid hide glue as having excellent creep-resistance.
- Polyurethane glue is not polyurethane finish. The coatings are a different product; see polyurethane finishes.
- Reactive glues have hazards a PVA does not. Gorilla's safety data sheet classes Original Gorilla Glue as 'Danger', a skin and respiratory sensitiser. Read the label and SDS of the product you use.
Water resistance comes in classes
'Water resistant' and 'waterproof' are not interchangeable, and both are makers' words. The class most wood glues are tested to is ANSI/HPVA Type I or Type II. Titebond explains both as tests on three-ply birch laminates: for Type II, specimens are soaked for four hours and baked, and must survive three cycles without delaminating; for Type I, they are boiled, baked, boiled again and sheared while wet, and must meet strength and wood-failure requirements. Titebond II meets Type II; Titebond III passes Type I, and Titebond calls it 'proven waterproof' — yet says both are not for continuous submersion or below the waterline. Gorilla calls its polyurethane '100% waterproof'. The Wood Handbook adds that polyurethane and epoxy bonds have limited resistance to repeated wetting and drying. A glue line that passes a water test does not make a whole project exterior-proof: the wood still moves, and the Handbook says cross-grain joints should be protected from changes in moisture content.
What strength figures mean
The Wood Handbook's finding is the useful one: an edge-grain joint can be as strong as the wood in shear along the grain, while an end-grain butt joint reaches only about 25% of the wood's tensile strength — see choosing a wood joint. 'Bonds stronger than wood' on a label is a maker's claim, and the test behind it matters. Titebond rates its wood glues by ASTM D-905 shear on hard maple — 3,600 psi for Original with 77% wood failure, 4,000 psi for III with 57% — and its cyanoacrylate by ASTM D-1002, a different test, at 2,800–4,200 psi depending on the substrate. WEST SYSTEM's 7,900 psi is the tensile strength of the cured epoxy itself, not of a bond. These numbers measure different things and are not a ranking.
Food contact
There is no general rule that cured glue is food safe. Titebond says Titebond II and III have been approved for indirect food contact and recommends them for cutting boards; its product pages word this both as 'U.S. FDA approved' and as 'U.S. FDA-compliant' for indirect food contact. That is a claim for those products and that use. The finish on a board is a separate question, covered in food-safe finishes; a full glue-up is the cutting board project.
- Using glue: surfaces, moisture, assembly times and clamping are in how to glue wood together; clamping pressure in clamps.
- Choosing a product: the makers' figures side by side in choosing a glue.
- When it goes wrong: failed joints and furniture repair in glue problems.
Choosing an adhesive family
- Indoors, damp, or outdoors — and the water-resistance class that matches
- A good fit, or gaps that need a gap-filling adhesive
- Working time needed for the assembly
- Whether the joint may need taking apart later
- Wood only, or wood to another material
- Hazards on the label and SDS
Sources
Family behaviour is from the Wood Handbook (2021). Product chemistry, classes, times and strength figures are each maker's for the product named, in its own words; 'waterproof', 'stronger than wood' and FDA wording are reported as the makers' claims. Strength figures from different test methods are not compared, and no adhesive is ranked.
- 1.
Chapter 10: Wood Adhesives: Bond Formation and Performance. USDA Forest Service, Forest Products Laboratory — Wood Handbook, FPL-GTR-282, 2021.
Used for: Table 10–1's adhesive families: poly(vinyl acetate) emulsions with high dry strength, low resistance to moisture and heat, and joints that yield under continued stress; cross-linkable PVA with improved moisture and heat resistance; polyurethanes reacting with moisture, gap-filling, with limited resistance to prolonged and repeated wetting and drying; two-part epoxies with limited pot life, low pressure needed, gap-filling, delaminating with repeated wetting and drying; animal glues often heated to apply, setting on cooling and loss of water, typically not water resistant; most wood adhesives not filling gaps well; flat, parallel surfaces for a uniformly thin layer; starved joints from overpenetration and squeeze-out; edge-grain joints able to be as strong as the wood in shear; end-grain butt joints reaching about 25% of the wood's tensile strength; 12% moisture content as a typical specification, with polyurethanes needing some water.
- 2.
Titebond Original Wood Glue. Franklin International (Titebond).
Used for: Titebond Original as an aliphatic resin emulsion; not intended for exterior use or where moisture is likely; ASTM D-905 on hard maple of 3,600 psi with 77% wood failure at room temperature.
- 3.
Titebond II Premium Wood Glue. Franklin International (Titebond).
Used for: Titebond II Premium as a cross-linking polyvinyl acetate meeting the ANSI Type II water-resistance specification; not for continuous submersion or below the waterline.
- 4.
Titebond III Ultimate Wood Glue. Franklin International (Titebond).
Used for: Titebond III Ultimate as an 'advanced proprietary polymer' passing ANSI/HPVA Type I, called 'proven waterproof' by Titebond yet not for continuous submersion or below the waterline; ASTM D-905 on hard maple of 4,000 psi with 57% wood failure; described both as 'U.S. FDA approved' and as 'U.S. FDA-compliant' for indirect food contact.
- 5.
Titebond Speed Set Wood Glue. Franklin International (Titebond).
Used for: Speed Set described as a high-solids PVA adhesive with the physical type 'aliphatic resin emulsion'.
- 6.
Titebond Genuine Hide Glue. Franklin International (Titebond).
Used for: Genuine Hide Glue as a natural protein solution in ready-to-use liquid form, with excellent creep-resistance in Titebond's description, whose sensitivity to moisture allows disassembly; not intended for exterior use.
- 7.
Titebond Instant Bond Adhesive Medium. Franklin International (Titebond).
Used for: Instant Bond as an ethyl cyanoacrylate setting in seconds, rated by ASTM D-1002 shear at 2,800–4,200 psi depending on the substrate; not intended for exterior use.
- 8.
Woodworking Glues — Frequently Asked Questions. Franklin International (Titebond).
Used for: The ANSI/HPVA Type I and Type II tests on three-ply birch laminates — Type II soaked four hours and baked, three cycles without delamination; Type I boiled, baked, boiled again and sheared wet; Titebond II and III approved for indirect food contact and recommended by Titebond for cutting boards; dried colours by product; Instant Bond softening slightly with water and designed for interior use.
- 9.
Original Gorilla Glue. The Gorilla Glue Company.
Used for: Original Gorilla Glue as a water-activated polyurethane that expands three times, called '100% waterproof' by its maker, with 'gap filling: no' in its own specifications.
- 10.
Original Gorilla Glue, Safety Data Sheet. The Gorilla Glue Company.
Used for: Original Gorilla Glue's hazard classification: signal word 'Danger', skin and respiratory sensitisation (diphenylmethane diisocyanate).
- 11.
Technical Data Sheet, 105 Epoxy Resin / 205 Fast Hardener. Gougeon Brothers, Inc. (WEST SYSTEM), 2014.
Used for: A two-part epoxy measured by volume or weight, with a pot life, a working time and a cure to working strength stated separately, thickened with fillers to bridge gaps; a cured-resin tensile strength of 7,900 psi (ASTM D-638), a property of the epoxy itself.
About this guide
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