Merz restoration

I have been restoring this lovely little Merz microscope, it’s a very special, rare microscope so I want to be careful not to over-restore it.

Below is a picture of it as it started out, as you can see it is fairly grubby. The stage has lost a great deal of its chemical blacking and there is verdigris on the foot where there is paint missing. There is no lacquer on the tube and the metal has become extremely dark. Of course, many people like the look of patinated brass, but to me, a completely blackened piece of brass is beyond a patina and certainly isn’t what the original maker would have wanted.

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Merz

The first step in the restoration process is to clean the microscope inside and out. Corroded screws and small parts were placed in an extremely mild metal de-corroder. Larger parts were cleaned carefully by hand using decorroder or pre-lim as appropriate. Below you can see the tube in various stages of cleaning. Note that once the tube is cleaned you can actually see the guide lines the engraver used to keep his lettering a consistent size!

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I have got to this point without using any harsh abrasives – no sandpaper, no polishing, nothing that removes any metal. Just de-corroder and pre-lim. Whilst there is still a very small amount of staining and a few small pits I did not remove them and went straight to a very, very, light straight-graining followed by lacquering.

The finished tube. You can still see the engraver’s guide lines and note that the un-lacquered parts of the microscope tube have been cleaned  but have not been polished or otherwise altered.

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Now for the paint, the paint is a mixture of dark umber and ochre pigments ground on a ground glass sheet with a muller. Linseed oil is added until a paste is formed, it takes a long time to get rid of all the lumps. The linseed and pigment paste is then thinned with tung oil and turpentine. Tung oil dries better than linseed alone and gives a higher gloss.

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I have not re-blackened the stage as I do not want to take away all signs of age and character. There are a couple of deep scratches on the stage though which look to be fairly recent and I shall probably blend them in a bit by blackening just the troughs of these scratches which are currently showing bright brass. I can do this by thickening the blackening chemical with PEG and painting it into the scratch marks with a  very fine artist’s brush in much the same way engraver’s fill their work.  That way it won’t affect the rest of the stage.

In the next post I shall show the reassembled microscope, right now the paint is drying.

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

Image result for Juglone

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!

Perfection! 

A small two tone Baker microscope appeared on eBay some years ago and I was quite taken with its beauty so when I happened across a very badly damaged Baker in need of re-lacquering I decided to recreate the two tone look.

This little chap has been something of an experimental piece as I have tested various brown and orange lacquers out on it. I am finally happy with it. I just have two small pieces drying and I can reassemble it properly. The slideshow below shows the microscope before and after restoration.

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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

 

The lacquering line

Lacquer drying

Not something you see every day -my lacquering washing line. It’s important not to touch the lacquer after it is applied. It needs to dry for several days before being cooked. This re-purposed Ikea wardrobe makes a fine drying cupboard. The wardrobe doors are a good cat deterrent too. Nothing worse than cat hair in the lacquer. I wonder how Victorian microscope makers kept their cats at bay?

I use stiff flexible lubricant hosing and crocodile clips to hold the work while I lacquer it. Once lacquering is complete I can bend the hose and hang it up in the wardrobe. Wire also works but the piece being lacquered can sometimes flop around too much, also wire is not unsuitable for tiny pieces like screws. 

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