Interesting chemistry of walnut hull inks and dye

Juglone, a brown dye, is found in several consumer products, including hair dye formulations and walnut oil stain. Juglone is an active ingredient in dietary supplements prepared from walnut hulls. Walnut hull extracts and poultices have been used for many years in folk remedies.

citation

Melting Point: 155 C (Merck, 1997)

Solubility: Slightly soluble in hot water; soluble in alcohol, acetone, chloroform, benzene, and acetic acid (Merck, 1997)

CHEMICAL IDENTIFICATION CAS Registry Number: 481-39-0 Chemical Abstracts Service Name: 1,4-Napthoquinone, 5-hydroxy-(8CI) Synonyms and Trade Names: Akhnot; C.I. 75500; C.I. Natural Brown 7; 5-hydroxy- 1,4-naphthalenedione;5-hydroxynaphthoquinone; juglone; regianin; walnut extract Structural Class: Bicyclic; napthoquinone

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It works!

So here we have it , black walnut dye in alcohol. It came out quite pale so I had to evaporate off the alcohol and resuspended in a smaller volume. I started with 100mls and ended up with about 5mls but it’s the colour I wanted. Tomorrow I shall add a few drops to some lacquer and job done!

Walnut adventures continued

The walnut hulls in alcohol have been on the magnetic stirrer for about 6 hours with intermittent heat. I’m not terribly impressed with the depth of colour. It looks okay unfiltered on paper but I am not convinced it will be dark enough once it is filtered. We shall see. I’ll give it until the end of the day before I filter.

Sadly , my magnetic stirrer heating element is not thermostatically controlled so I can’t leave it on the heat unattended. I have to keep an eye on it. Makes for a rather boring day. I may concentrate it down after filtering. ideally it will be dark enough that I can just add a few drops to my usual lacquers to tone them down when necessary. I hope it’s worth it. I had high hopes.

Very impressed

I’m still waiting for my walnut hulls to arrive (damn you bank holiday) but I thought I’d try mixing some alcohol dyed with coffee in with some lacquer while I wait. I am NOT going to use coffee in microscope lacquer but it does give me an indication of the kind of colour I might achieve when the walnut arrives. Coffee in the lacquer gives exactly the colour I want. Hurry up Post-lady! Bring me my walnut!

Different lacquer colours

By varying the amounts of various ingredients, such as Dragon’s Blood, various lacquer colours can be achieved. Below is a picture showing three different batches of lacquer I have made applied to microscope parts.

I am about to make up a fresh batch of yellow as I have a piece to lacquer for a customer, I have some leftover yellow lacquer but I don’t want to risk using it. The lacquer ingredients are dissolved in pure ethanol, over time the ethanol takes up water and water is death to lacquer. Any water in your lacquer and you will get cloudiness and a nasty finish. It’s less trouble to make up fresh.

lacquer colours

Yellow, brown and gold lacquer

 

Brown lacquer

Today, I have been working with an unusual brown lacquer. Brown lacquers were not used a great deal, but it is good to have finally perfected one for those rare occasions when a brown lacquer is called for.  The lacquer uses garnet shellac and is somewhat more tricky to apply than any of my yellow or gold lacquers. It is a fairly muted brown and needs to be applied in a slightly thicker layer than usual. Also, it is a damp, cold, dull day and lacquers are much easier to apply when there is bright light and low humidity.

It’s looking good, I am eager to see what it looks like once it has dried and has been cooked.

garnet shellac lacquer

Brown lacquer applied to microscope limb