Hide Glue for Wood Finishing

Hide glue is glue made of animal. This glue is an adhesive material that has been known and used a long time ago; it could be since the prehistoric; probably it is the oldest type of glue. Long time ago, people used the fat and protein from animals to paste the wood or any other stuff. Now the glue is marketed in the small granule form and used for some special purposes in some industries. The modern process is used in the hide glue industry, but the source is still the animal. The collagen from the skin, bones, and tendons of cattle or horses is hydrolyzed to make the glue particles.

The uses of hide glue in the woodworking industry have been much reduced since the invention of the glue from synthetic material. Today, animal glues are still used for making music instruments and restoring objects, paintings, illuminated parchment manuscripts, and other artifacts.

The glue can also be used in the wood finishing. Some people use the hide glue to make some finishing effect, and some others use it to caress the wood veneer.

hide glue (the picture is from wikipedia)

Here are some uses of the hide glue in the wood finishing.

• Glue sizing.

Hide glue can be used to overcome the problem of cracking veneer. Some types of veneer, such as crotch or burl, have a high risk of getting crack problems. They tend to have high movement according to the moisture content changes. You can use the hide glue to do glue sizing to avoid the veneer cracking. The glue will cover and close the pores and grains and make the wood moisture content to be more stable. By this way, the crack problem can be minimized.

The application of hide glue to glue sizing is done as follows: 
 
The wood veneer should have been attached to its core and has been sanded well. The veneer surface has to be cleaned from the tape marks, glue marks, or scratches.
Mix the hide glue with water in the ratio 1:1, then boil the mixture until all the granules melt to form a liquid paste. Then layer the warm glue evenly on the veneer surface. Use a putty knife to apply the glue to the veneer surface (as you apply the wood filler to the wood); avoid too-thick glue. The glue should be left only at the inside pores and grain; the excess glue at the surfaces must be cleaned. 
Let the glue dry for about 1 hour. The glue will get cold and hard. After the glue is hard, then we can sand the veneer surface to make flat and smooth surfaces. Then the veneer is ready for the finishing process. See our previous article: oak burl finish

The glue will fill and close the pores of wood grain and pores to make more stable veneer, and then the veneer movement will be minimized. 
The glue sizing will affect the absorption of stain by the wood veneer. Therefore, glue sizing should only be done selectively on the veneers that really need it. Usually it is used to care for the burl or crotch that has a high risk of getting cracking problems. The regular veneer normally does not need the glue sizing. 

Crotch mahogany veneer cabinet

• Hide glue to make a crackle finish.

There are many ways to make a crackle finish; one is with the hide glue. Crackle finish with hide glue will produce a crackle effect with a large crack and can be set at the desired place.

Here's how to make a crackle finish with hide glue.
Mix the hide glue with water and boil until it is melted, as in the processing of hide glue to glue sizing. Then apply (brush) the hide glue on the wood surface. Apply glue to the parts where the crackle effect is desired, then layer the water-based paint on the wood surface. Water-based paint application should be done by way of spray and evenly to all surfaces. Let the water-based paint dry together with the cooling of the hide glue, and then the paint on the hide glue will crack.

Then the finishing process can be continued with the application of sealer, glaze, or stain to produce a more attractive crackle effect.

• Hide glue to make a gesso finish.

You can also make the use of hide glue. Mix: 5 parts of hide glue, 5 parts water, 1 part of calcite and 1 part of talc and boil the mixture until it melted and form a liquid paste. Use this liquid as a “gesso” for various purposes. It can be used to form a flat surface and smooth as the preparation to make a high-gloss paint finish. It can also be applied to make a texture effect by the technique application.