Glue and Adhesives
GUIDE TO CHOOSING GLUE & ADHESIVES
music for glue work. I think these guys were huffers http://youtu.be/6kpYUuHMhkg
Any glue will benefit from being applied to clean uncoated surfaces. In most cases this means abrading the surfaces to give the glue 'tooth' to grab. Most glues do not adhere well to itself so requires removal of old glue before new is applied. This is especially true of wood glues (yellow and white)
White glue : The most common glue. Think Elmers Glue. Good for wood, paper, cardboard, cloth, and many porous and semi porous materials. It's easy to use and clean up and very safe. The glue requires minimum ½ hr. clamp time for wood and achieves full strength in 8 hours. Good all purpose glue. Dries clear.
Yellow glue : Aliphatic resin (AR) glue. Titebond is one of the brand names and is what is provided in our tool crib. Thicker and creamier than white glues. Especially good for wood projects but can be used on other porous and semi-porous surfaces. Comes in interior (most common) and exterior (more water and moisture resistant (but not waterproof!!) Dries with a yellow tint. ½ hour clamp time and full strength is achieved in 8 hours.
Hide Glue. Before there was white and yellow wood glue there was hide glue. It is a glue made from boiling 'animal connective tissue' (cartilage, bone, hoof). Now rarely used. Was extensively used in making musical instruments because it had good hold and because the bond could be broken with steam so that the instruments could be repaired and then reglued without damage or severe sanding of the joints.
Polyurethane Glue : Gorilla Glue. This one is a waterproof adhesive. It bonds to almost everything; wood, metal, ceramics, plastic, stone etc. Slight dampening prior to adding the glue is recommended for most surfaces. This glue foams and expands so is ideal for filling gaps and for poor fitting parts. It expands enough that the glue can push glued surfaces apart as it sets up so clamping is a must. Because it expands use less rather than more & you'll learn. Cleanup is with mineral spirits which can also be used on the excess foam. After drying excess foam can be cut away or sanded down. Once the bottle is opened air starts to set up the remainder so shelf life is shorter than other glues (months). 24-hour drying time for full strength.
Epoxy : Epoxies are two part adhesives you mix together in equal parts. They come in both semi-liquid and putty style. Epoxies stick to almost anything and are especially good at bonding dissimilar materials together. They are great for filling gaps and dry hard (hard enough that they are difficult to sand so don't be too generous). The semi-liquid varieties come in various setting times (e.g. 5 minute, 30 minutes, 1 hour) which reflect the working time before they start to set up. The longer the working time the stronger the bond usually. Full strength is achieved in hours no matter the setup time. Clean-up before set up is mineral spirits, after with lacquer thinner. Bond can be broken with heat.
Cyanoacrylate. Cyanoacrylate or CA glues. Commonly known as instant glues. Super glue is the most common product name. They come in thin and thick bodied. CA glues dry very quickly, and they work well on a wide variety of both porous and nonporous materials. CA adhesives are available in different thicknesses, and each one will have different gap-filling capabilities. You can also purchase an accelerator, which will dry the glue almost instantly, and solvents, which are highly recommended for ungluing stuck fingers. Can be removed from fingers etc with acetone.
Contact Cement : Contact cement is a glue applied to both surfaces, that when dry the items are pressed together for a permanent bond. Contact cement is best used on non-porous surfaces that have a tight (flush) fit. Somewhat like a liquid Velcro. Think laminate on a table or countertop. Contact cement comes in solvent and water based versions. The major difference is that the water based takes longer to dry prior to bonding and the solvent based has a very strong odor. Application is by roller or brush, importantly an even coat needs to be applied. After bonding pressure must be exerted on the surface usually with a J-shaped roller. Can be undone with an iron and scraper. For gluing foam sheets together the water based type needs to be used because the solvent based will eat the foam. For gluing foam, rubber cement applied to both surfaces and allowed to dry will act as a contact cement.
Construction Adhesive : Thick, sold in tubes that fit in standard caulking guns. Used to bond a wide variety of common construction materials such as wood, masonry, metal, ceramics, foam insulation and drywall. There are different types for different purposes. Can be used to fill gaps although does not expand to do so.
Hot Glue. It is a form of thermoplastic adhesive. Comes in rods of 1/4" and 1/2" (most common) and is melted and dispensed from a 'hot glue gun'. It is a high tack adhesive. Good for a number of applications including both porous and nonporous surfaces. Very safe, very low VOC. Industrial versions can further be cured by ultraviolet light or come in urethane form which cures further from exposure to moisture but versions available to the general p[ublic are limited to curing during cooling. Disadvantage is that heat can undo the bond.
Plastic Adhesive. Some plastics are almost impossible to glue. Polypropylene which has a slightly oily feel (toys, chairs, etc) is great because it is slightly flexible and wear resistant but those qualities also make it hard to glue. There are special epoxies for the purpose, but my experience is they don't last. Acrylics can be glued with super thin liquids that are based on methyl chloride (acetone can also work) that are applied to a tight joint. The glue actually melts the plastics in the joint together.
Other Adhesives. Silicone and acrylic-latex caulk can be used as an adhesive. Disadvantage is that they take 24 hours to fully set up and are thick bodied. Both will work on dissimilar materials. Silicone is flexible and waterproof when dry and would have to be cut away or cleaned with lacquer thinner or acetone after setting up.