Technical Gelatin, sometimes referred to as gelatine, is made from pork skin. Sheet or plate gelatin is sometimes preferred over granular or powdered animal glue, because it results in a clearer, more transparent product. This makes it ideal for use in gilding. Gelatin is preferred by many professional gilders over hide glue, because it can take a burnish easier than hide glue when mixed with gilder’s clay, chalk or gesso.

As with hide glue, gelatin glue is graded and sold by its Bloom Value or Bloom strength. Bloom value is a measurement of the strength of a gel formed by a 6 and 2/3% solution of the glue that has been kept in a constant temperature bath at 10 C for 18 hours. A device called a Texture Analyzer or Bloom gelomater is then used to measure the weight in grams required to depress a standard plunger 4 millimeters into the gel. If this procedure requires 200 grams, then the glue is a 200-bloom value glue. Glue is also tested for its viscosity at this same 6 and 2/3% concentration. A standard viscosity range is associated with each bloom level. Technical gelatin has a bloom value of 100-110 mg. The bloom measurement refers to the elasticity of a gelatinous mass. The higher the number the greater the elasticity.

So, technical gelatin dries clearer, but has less elasticity of the gelatinous mass.  Therefore, full strength technical gelatin is best used in painting hard surfaces that remain stationary hard.

Again, the majority of the text was extracted from various supplier links, including http://www.naturalpigments.com; https://www.asianproducts.com/hotproduct/manufacturer_handicraft-making.htm; http://www.indiamart.com

Attached are examples of technical gelatin sheets and powder.  The technical gelatin that I have used in the past came in the form of a very fine powder.

Technical Geltain Sheets

Technical Gelatin Powder

Most high-grade glue is made from pure bovine hides. The glue is manufactured from the protein collagen found in skin, connective tissue and bones of animals.

Like rabbit skin glue, bovine hide glue provides a low cost, easily formulated paint that is called distemper. Diluted with water, it is good for color sketching, as well as for painting. Distemper paintings have lasted for centuries without change.

Rabbit skin glue is much stronger than most hide glue and also has a greater expansion rate when water is introduced prior to cooking.

The following hide glue specifications are from the product sold by Natural Pigments:  “Hide glue is graded and sold by its Bloom Value. Bloom value is a measurement of the strength of a gel formed by a 6 and 2/3% solution of the glue that has been kept in a constant temperature bath at 10� C for 18 hours. A device called a Texture Analyzer is then used to measure the weight in grams required to depress a standard plunger 4 millimeters into the gel. If this procedure requires 200 grams, then the glue is a 200-bloom value glue. Glue is also tested for its viscosity at this same 6 and 2/3% concentration. A standard viscosity range is associated with each bloom level. Its low bloom value gives it a longer setting time, making it ideal for use in gesso and for sizes (the bloom value refers to the strength of a gel formed by a 6 and 2/3% solution of the glue kept at a constant temperature- the higher the number the greater the strength of the glue).

Hide Glue Recipe:
The standard recipe is one part glue to ten parts water. First soak the granules in water for 30 minutes and then heat gently in a water bath until completely dissolved (for about 30 minutes to one hour – allowing it to bloom).  Warm this swollen glue by placing the container in another vessel filled with hot tap water. This will cause the glue to completely dissolve. Never heat collagen glue over 140 F.

Here is the link for the text in it’s entirety http://www.naturalpigments.com/hide-glue.htm

Double boiler for glue, water and granulated hide glue

 

Once granules lave liquified.

 

A chart that I stumbled across online that places glue within a context of other binders for woodworking.

 

A great material context and summary for hide glue.

Rabbit Skin Glue is a high grade glue made of pure rabbit collagen. It is a granular glue that is easy to dissolve in water for use as a size in preparing canvas and panels and in distemper painting. It easily dissolves in water. This makes it ideal for use in gesso and as a medium for distemper painting.

Stronger than most modern adhesives, rabbit skin glue is used in traditional woodworking, gilding and painting techniques. First soaked in water and then heated in a water bath, it is applied warm, and gels when left to cool. In woodworking, rabbit skin glue’s solubility in water makes it reversible, while its “open time” allows for repositioning. In painting and gilding techniques, it is used both as a size for canvas and boards, in recipes to make traditional gesso, and in distemper paints.

Animal glues vary in strength, but rabbit skin glue usually offers the highest strength, viscosity and elasticity. True rabbit skin glue tends to gel at lower temperatures, making it easier to use in gesso applications. Otherwise, glue made from bovine collagen are comparable.

 

Initially the hides are kept in a lime slurry pit for 1-3 months for lime curing. This process helps loosening of collagen bond in hides so that it can be extracted easily. After lime curing the hides are washed several time to remove excess lime and than the glue is extracted from by cooking in boiling water. The extracted glue is then concentrated with the help of an evaporator. The concentrated glue is dried in drum driers and pulverized for final packing.

Animal glues are adhesives that are high molecular weight polymers in organic colloid form from hydrolyzed collagen found in animal hides, connective tissues and bones. Glue contains two groups of proteins: chondrin, which accounts for its adhesive strength, and gluten, which contributes jelling strength. Animal glue is derived from the simple hydrolysis of collagen, which is the principle protein constituent of animal hide, connective tissue and bones.

Hide and bone glues make up the two major types of animal glue. Hide glue, which is by far the superior of the two, yields a fairly neutral pH in solution, usually in the range of 6.5 to 7.4, although wider variations are possible. Bone glue is generally acidic, having pH values of 5.8 to 6.3. A glue having a high acidity absorbs less water and tends to set more slowly than a glue having low acidity.

Animal glue is soluble only in water and insoluble in oils, greases, alcohols and other organic solvents. When placed in cold water, the glue absorbs water and swells to form a gel. When heated the glue dissolves to form a solution. When the solution is cooled the glue once again forms an elastic gel. This property is thermally reversible and upon application of heat the gel liquefies. The gelling or melting point of an animal glue solution can vary from below room temperature to over 48.9° C (120° F), depending upon the grade, concentration and presence of modifiers in the glue.

A side note to provide context:  Animal glues have been in use since ancient times. Paintings and murals from the period between 1500-1000 BCE show details of wood gluing operations. A casket removed from the tomb of King Tut shows the use of glue in its construction. Many art objects and furnishings from the tombs of Egyptian pharaohs are bonded or laminated with some type of animal glue. The first references in literature concerning glue providing simple procedures for making and using animal glue were written about the year 200 BCE.

Much of the original development of adhesives based on natural products has come in the woodworking and paper industries. Prior to World War I, there were simply no other options. The five classes of adhesives used most were animal glues, liquid glues (lower strength variety of fish or animal glue stabilized with acid for a long term storage), casein and vegetable protein glues, starch glues, and blood albumin glues. Also used to a lesser degree in adhesive formulations at the time were sodium silicate, mucilage, asphalts, gums, shellacs, and natural rubber.

The above information was found on a suppliers site.

http://www.naturalpigments.com

Here are a few images of how the product is stored and shipped.

 

 

“At one time in history, the English word pink referred to a yellow color.

Interesting side note: There is speculation, owing to its greenish yellow tone, that it is derived from the German word pinkeln translated in a dictionary of 1798 as ‘to piss, to make water.’

The color most often known as Dutch pink was ‘a yellow lake prepared from Persian berries or from quercitron and used chiefly as an artist’s pigment,’ according to Webster’s Third New International Dictionary, under the definition of Dutch pink. This color was ‘a light yellow that is greener and slightly darker than jasmine and greener and stronger than average maize or popcorn—called also English pink, Italian pink, madder yellow, stil de grain, yellow madder.’

When we review the literature on Dutch pink, we find that it is a lake pigment made from various organic sources, the most often mentioned is Rhamnus or buckthorn berries. These pigments also contained other yellow dyes, such as fustic, turmeric, weld, dyers’ broom and dyer’s oak. Chemically, the colorants of all these yellow dyes are types of aromatic molecules known as flavonoids. The various yellow dyes all have a very similar appearance and were probably used indiscriminately by color makers and artists.

Note what Robert Dossie in Handmaid to the Arts wrote about Dutch pink:

Of Dutch pink.
Dutch pink is a pigment formed of chalk, coloured with the tinging particles of French berries or other vegetables. It is principally used for coarser purposes in water ; not bearing well to be worked in oil : nor can it be depended upon with regard to its standing so as to be fit for paintings of any consequence.”

This excerpt was posted by Linda N. and can be found in its entirety at: http://www.naturalpigments.com/art-supply-education/pink-was-yellow-paint/

My opinion: I absolutely love Dutch Pink. My favorite use of Dutch Pink is adding it into a variety of sky colors. the color has more depth than Yellow Ochre or Raw Sienna, yet is richer that yellow madder or stil de grain.

Below are examples of Persian Berries, Common Buckthorn Berries, Quercitron nuts, and the powdered extracts that each produce. I have also included a “stil de grain” powder pigment image for contrast and comparison.

 

Persian Berries (Buckthorn Berries – not the common type that are deep blue as below)

Chene Quercitron nuts

Persian Berry Powder/Dutch Pink Pigment Source

Quercitron Powder/Dutch Pink Pigment Source

Stil de grain pigment/yellow madder color

“Of supreme importance in painting is the true understanding of values.  Color is at all times. comparative, and values cannot be determined in any way by comparison.

If we takes white and add a pinch , we produce gray, which compared with the white is a value.  Add to this value a pinch of black as before, which will produce a trifle lower than tint, and we have what is termed a second value.  This value, with a pinch of black added, will produce a trifle deeper gray; and we can proceed this until we reach deep, or low, gray, and lastly black itself.  Now if we lay the values thus proceeding in small planes close to each other, with their edges touching, we can lightly soften these edges with a dry badger blender without interfering with the individual purity of each value and thus produce an agreeable gradation of values ranging from black to light.

With these values set upon the palette, we could render a drawing in black and white which would be suitable for reproduction in a magazine or book illustration and whose proper name would be monotone.”

Excerpt from Frank Atkinson’s “Scene Painting and Bulletin Art” (1916, page 11).