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Glue Choices And Uses – Part 1 by Philip Hodge
Collagen basedAnimal Glues
Pearl Glue – The strongest of the animal glues. It will stick a variety of materials including, wood, metal, ivory etc. It is reversible so ideal for all joints that may need to come apart in the future. The The disadvantage of having to use it hot is balanced by the immediate grip you get. Long shelf life when in pearl form, but will go mouldy if not regularly heated up when in the pan. To use, put a quantity of the pearls in a container eg a) top pan of a bain marie, b) a jar inside glass jar or c) tin can.Add water until it just covers the pearls. Leave to soften for at least 20 minutes. Then put on to heat protected from direct heat by surrounding water e.g. using a) bain marie, B) baby bottle warmer or c) saucepan with water in.
Sheppey Tug – A little more expensive than pearl glue and not quite as strong. Used hot as per pearl and also reversible. The main advantages are that it comes in a jelly form so if you don`t use it very regularly you can cut off just the amount you need and melt it down to use from a double boiler. It also contains a fungicide so will not go mouldy.
Liquid Hide Glue – It`s strength is reduced by the additive that keeps it fluid but it is still quite a strong glue. It`s main advantage is in those situations where you need a bit more time to work as it is used cold. As with all animal glues it can be re-softened if required. You can buy this from a wood finishing suppliers if you wish ( beware of how long it is since it was made, as it does have a limited shelf life ) or you can come on a restoration course and ask me to show you how to make your own.
Fish glue – This is the most expensive of the animal glues and is not so widely available. It`s main advantage is that it is used cold and is therefore very useful for those instances when you need a little more time to work. Recipes for making it vary with the most common being derived from the skins, bones and swim bladders of fish. It gives a strong bond when dry but I don`t think it is quie as strong as Pearl glue
Rabbit skin Glue – The clue for what it is made from is in the title. It is reversible. It is usually used in specialist areas such as gilding. It can be adjusted to different strengths by the addition of more or less water. It is used hot but has the advantage at low strengths that it is useable at relatively low temperatures.
Glue Choices And Uses – Part 2 by Philip Hodge
Modern Glues
PVA – Or to give it its full name Polyvinyl acetate, is probably the most widely available modern glue. There are different types but principally you need to know that the strongest (waterproof and heatproof) type is sold in blue containers. This type is non reversible whereas standard pva is thermotropic, ie it can be reversed by applying heat. This use of heat can of course, if you are not very careful, damage surrounding finishes. Another danger with PVA is that it can “creep” i.e. after you think that the glue is dry the glue can push the 2 corresponding faces out of position. It is useful for gluing on baize.
Polyurethane Glue – This is sold in pots but is commonly sold in tubes for use with an injection gun. Gorilla glue is an example of a polyurethane glue. It has a relatively short life after being opened as it dries by reacting with moisture whether in the air, or in the material to which it is applied. Therefore I recommend the tubes over the pots as it is more protected from the air. Beware of the fact that even if you stop pulling the trigger it will continue to ooze out of the tube`s spout so have the top of the tube or a convenient screw handy to plug the end. This is because this is an expanding glue and it will continue to foam while it dries. If you haven`t properly clamped the items they will always push apart leaving an unwanted gap of glue and your wood out of position. This is a major problem as this glue is both very strong and irreversible. This is a plus factor for some situations but an unwanted problem if your wood is not in the desired postion. As with any glue make sure that you do not glue either your clamps or your flat blocks to your workpiece by putting some greaseproof paper in between. The expansion has advantages when internal gaps need filling. Also wear gloves so not to get this glue on your skin. As far as I know it does not have any major health risks and it certainly doesn`t burn, but it does turn the skin black and despite concentrated washing it stays that colour for up to a week.
Cascamite – Specifically formulated for exterior joinery exposed to weather. This adhesive produces a bond stronger than the timber itself. The powder system gives extremely good gap filling properties, ensuring rain does not enter the joint. Use externally where a high bond strength/gap filling is required. It has little to offer for cabinet making or restoration unless you are dealing with items that are to be exposed to the elements but even then I would prefer to use Polyurethane glue. It is non reversible. As it is a powder uou also have the problem of mixing it to the correct consistency.
Contact adhesive – Such as UHU or Bostik. This dries to a rubbery finish and is pretty useless for gluing joints etc and a nightmare when it comes to restoration. It`s main useful use is for gluing on gimp or rope trim to hide upholstery tacks on chairs.
Superglue (Cyanoacrylate) – Only occasionally useful on furniture. Chiefly it is useful when gluing metal to wood although animal glues can also be used for this. It is my experience that a lot of the superglues that are sold today do not have the same sticking power as when they first came on the market so this is something to watch out for.
Hot glue gun – messy, inaccurate plastic looking glue – Avoid!
Proprietary polymer glue – eg Titebond. On the plus side it has a fast set which shortens clamp time, Bonds stronger than wood, it has good heat and solvent-resistance and sandability, it is easy to clean up with water. On the minus side it is irreversible, it can yellow when exposed to UV light, it`s rigidity means that any movement in the wood will always result in the surrounding wood splitting rather than the joint.
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