Hide glue for wood finishing

hide glue (the picture is from wikipedia)

Hide glue is glue made from animal. This glue is an adhesive material that has been known and used since long time ago since the prehistoric; probably it is the oldest type of glue. Long time ago, peoples has used the fat, protein from animal to paste the wood or any other stuff. This time the hide glue is still produced with the modern process. The collagen from skin, bones, tendons of cattle or horses is hydrolysis to make the glue particles. The glue is marketed in the small granules form.

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 instrument and restoring objects, paintings, illuminated parchment manuscripts, and other artifacts.

The glue also can be used in the wood finishing. Some peoples use the hide glue to make some finishing effect and some other use it to care the wood veneer.

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: crotch or burl, have high risk to get crack problem. They tend to have high movement according to the moisture content changes. We 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 then the crack problem can be minimized.
The application hide glue to glue sizing is done as follow:
The wood veneer should has 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 to the veneer surface evenly. Use putty knife to flatten the glue, avoid too thick glue at the surface. The glue should be left only at the inside pores and grain; the excess of glue at the surfaces must be cleaned. 
Let for awhile (about 1 hour) to let the glue layer to become cold and hard. After a layer of 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 on the veneers that really need. Usually it is used to care the burl or crotch that has high risk for cracking problem. The regular veneer normally does not need the glue sizing. 

 crotch mahogany veneer has high risk to get crack

• Hide glue to make crackle finish.

There are many ways to make crackle finish, one is with the hide glue. Crackle finish with hide glue will produce crackle effect with a large crack and can be set at the desired place.
Here's how to make crackle finish with hide glue.
Mix the hide glue with water and boil until it is melted as in the processing hide glue to glue sizing. Then apply (brush) the hide glue on the wood surface. Apply glue at the parts where the crackle effect is desired, then layer the water based paint to 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 gesso finish.

We can also make the use of hide glue gesso. 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 to the base for high gloss paint finish. It can also be applied be used to make texture effect by the technique application. See our previous article: high gloss silver finish