Hide Glue - Part #2: Working with Hide Glue Granules

Working with traditional animal glue is an extremely simple operation. Don't overthink the process and you will be fine!

Your two common Gram Strengths or "Bloom Strengths" are as follows:

180 Bloom Strength Hide Glue:

• Long open time
• Strong bond
• Also known as "Marqueter's Grade" or "Veneer Grade".
• Medium initial tack
• The ultimate glue for marquetry, parquetry and all veneering work.

250 Bloom Strength Hide Glue:

• Short open time
• Very strong bond
• Also affectionately known as "Cabinetmaker's Grade".
• The preferred glue for piano and organ technicians.
• Fast initial tack
• The best cabinetmaking grade hide glue.

In it's dry granular form, hide glue has a completely unlimited shelf life when stored in a dry container and kept away from heat and moisture. (I have cooked up hide glue from 38 year old granules and it worked perfectly).

To prepare the glue for use, you simply add the granules to warm water and stir in. Limit your heat to less than 64 degrees.

A general guide is to mix using 1.8 parts water to 1 part granulated glue. Adjust to the consistency of varnish.

Brandon's Tip: Lay your hands on a few ice block trays. Mix up sufficient glue to fill all the cubicles. Let them sit overnight to gel and then pop the trays in the freezer. Once the block are properly frozen, pop them out into a suitable container and keep them in the freezer. Repeat the process a few times and you will have enough "Ready To Warm" Hide Glue for a few months!

(Be sure to mark the container clearly, as hide glue tastes really odd in a gin & tonic!) Making and freezing the blocks eliminates the overnight wait completely. When you want to cook up some glue, simply grab a few blocks and head for your workshop!

Also, when you have finished with your glue and don't want to waste it, simply pour it back into the ice trays, let it cool and freeze it again into blocks for later use!

• To warm up the glue you need a double boiler (that kitchen thingy that granny used to heat milk in).
• Traditional cast iron double glue pot.
• or you can use my cheap favourite...a baby bottle warmer. Set to 60º.

A Double Boiler that was commonly available in SA, made by Hart.

Brandon's Tip: For daily use in my workshop, I rely on a cheap thermostatically controlled baby bottle warmer from Clicks and a glass jar which fits inside allowing a small space around the jar for the water.

You need to bring the glue up to a reasonably constant temperature of 145º Fahrenheit (60º Centigrade). A couple of degrees cooler is not a train smash.

A few degrees hotter may impede flow.

If for some reason, your glue goes dramatically over this standard temperature, throw it away, as you have more than likely broken down the protein chains and rendered it useless.

Brandon's Tip: Cover your jar with a piece of aluminium foil (shiny side down) and fold the edges so that it forms a lid covering the entire bottle warmer. This will keep most of the moisture in, reducing the need to monitor and top up the water jacket. Just poke a hole with the digital cooking thermometer to go through the foil lid and you are all set.

The odour of the glue can be quite unpleasant. This is normal.

To help the mixture to run nicely without lumps whenever you make a batch, or reheat a batch, add 6 drops of methylated spirits and stir in briskly.

The viscosity of your glue mix is easily measured by lifting your glue brush about 300mm above the glue jar and letting the hot glue drip back into the jar. It should be thin and liquid with no clumps. Once all these precautions have been taken, if you lift your stick from the reservoir and the glue is clumpy and forms a skin which wrinkles and un-wrinkles as you watch, your glue is a little overheated. 

You can easily test the strength of your glue by putting a small amount between your finger and thumb and rubbing them together until the glue cools. You then measure the strength by slowly pulling your thumb and finger apart to create a gap of about 4-5cm, and observe the protein strands which will look like very fine spider webs. The longer the strands...the stronger the glue. It's that simple!

When it has been freshly cooked, the colour of protein glue is a light amber shade, and it will continue to darken the longer it cooks. As long as you do not overheat your glue batch, it will remain immensely strong.

Brandons Tip: If you have any prepared glue left over, just put the jar in the fridge overnight and you can reheat it and continue to use it the following day or for any reasonable period thereafter. Rather freeze if you know you'll not get back to it within a week.

Animal glues are the only easily reversible glues available to woodworkers.

All modern synthetic glues convert from one state to another state by using a catalyst. Once converted, the adhesives are for the most part, impossible to undo. Since protein glue reacts to heat and moisture, it can easily be converted from liquid to solid and back again, even after a century or more!

This is the primary reason as to why hide glue is used continuously in the field of antique furniture restoration. The existing glue can be softened and cleaned off with warm water and a new application of hot hide glue will completely bond with the previous glue and the wood.

Glue reversibility is also of essential importance when working with veneers, inlays and marquetry surfaces. When you are building up a pattern or picture of wood pieces on your substrate, it becomes necessary to glue and unglue, and shift pieces into place as you progress, only hide glue allows you to do this competently.

Hide glue also allows easy repair and replacement of damaged veneers on furniture, by using heat and moisture. 

Also, don't forget the fact that hide glue does not exhibit the dreaded "creep", that synthetic adhesives do when clamping boards together, due to its high initial tack.

Another of the wonderful attributes of hide glue is that it's incredibly easy to clean it off your wood surfaces, either with a little water, by sanding or by using a cabinet scraper. 

Most importantly, hide glue does not show up underneath your finishes! Stains, oils and sealer take on top of hide glue.

Loosening or removing hide glue is dead easy! One could use warm water or a blast of steam and remember that you can quickly loosen it using vinegar (brown or white) and also for clean up.

Hide glue is nearly 100% protein and as such combines with wood at a molecular level, bonding molecule to molecule which qualifies it as a glue. PVA glue such as Alcolin is strictly an 'adhesive' as is rubber glue or contact adhesive.