Hartnack to RMS nosepiece

I was asked to make a new nosepiece for a Hartnack microscope which would enable the owner to use RMS objectives as he finds Hartnack objectives very fiddly. The Hartnack has a small diameter male Thury thread whereas the RMS is a larger female Whitworth thread. The nosepiece maintains the tube length but the Harnack has an adjustable tube length anyway and the new nose piece works just fine. As you can see there is quite a difference in the width where the objective attaches. The new RMS nosepiece looks a little clumsy compared to the original.

hartnack nose2edithrtnack nose1

Verick 1 – Brasso 0

Oh the poor little Verick! In a photograph there didn’t seem much wrong with this Verick apart from the total lack of lacquer but it had serious issues. The  Tube holder was stuck fast, the tube was stuck fast in the tube holder and it took several hours to get it all unstuck. The cause? Brasso. Don’t use brasso on your microscopes, it removes the lacquer and clogs up the moving parts it’s like glue. Below is a picture of the aperture ring which was also stuck fast and what it looked like inside when I finally got it apart.

brasso 2

There is hope though, if you can get the microscope apart the brasso can be removed quite easily. Here is the little Verick before and after lacquering, all parts are now moving smoothly and it is ready to return home.

Verick2

Verick frozen solid with brasso

IMG_8077

After cleaning and lacquering

IMG_8079

After lacquering

Plossl restoration

This beautiful little Plossl had been mistreated, either stored in an attic or garage, or otherwise abused. Very little lacquer remained and that which did was decaying casuing corrosion and pitting to the metal. I have stripped off the old lacquer, removed the corrosion and polished without removing all the scratches and pitting that show the age and history of the microscope. They are simply safely locked away under new lacquer which should protect it from any further degradation. I have not lacquered the mirror or the objective as the risk of damage to them by polishing and hot lacquering was quite great. I’m rather pleased with it.

IMG_20200105_152959

 

 

 

 

Silvering mirrors

Today I’m preparing to silver a mirror. I use the Rochelle salt method as follows:

Solution 1: Silver nitrate 2.48 grams, silver nitrate 2.07 grams, distilled water 473mls, 25% ammonia as required.

Dissolve 2.48 grams of silver nitrate in 120mls water stirring with a glass rod. Add around 30 drops of ammonia, the solution will go dark and will then gradually clear again.  Once the solution is clear add the rest of the silver and swirl until dissolved. Add the remaining water. Leave to settle for an hour or two then filter and store in a dark bottle labelled Solution 1.

Solution 2: Rochelle salts (potassium sodium tartrate) 1.56 grams, silver nitrate 1.62 grams, distilled water 473mls.

Add 1.56g rochelle salts to water in a glass vessel and bring to the boil. After boiling for 1 minute add the silver nitrate and boil for a further 5 minutes. Leave to cool then filter and store in a dark glass bottle labelled Solution 2.

IMG_20200121_162016

Thoroughly clean and de-grease the glass to be silvered and tape up any areas on which silvering is not required. Warm the glass to about 38C with warm distilled water, when warm, drain off the water and cover with a 1:1 mixture of solutions 1 and 2. It is best to warm the solutions before mixing them together. Swirl the mixture over the glass for around half an hour then pour off the solution, rinse in distilled water and leave to dry. Gently paint the back of the mirror with a suitable paint to protect it from abrasion.

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.

20170827_152550

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!

This slideshow requires JavaScript.

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.

This slideshow requires JavaScript.

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.

This slideshow requires JavaScript.

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 mechanism inside the little brown Merz

The Merz has an interesting design, and not one I have seen before. Most microscopes of this age and style have a solid round  bar through which a triangular bar passes. The triangular bar has a screw at one end and a spring at the other and it’s a very effective, simple fine focus mechanism.

The Merz has a rather different set up – it also has a triangular block with a screw at one end and a spring at the other, but instead of passing through a round bar, the triangular block passes through another triangular piece. The outer triangle is constructed from pieces of flat brass which have been joined together by brazing – this might explain why Merz painted these parts rather than lacquering them I think. Using brazed pieces of brass would have saved a lot of wastage and money and it would easily have been strong enough.

A “typical” round Baker fine focus block on the left, the Merz brazed, triangular fine focus mechanism on the right.

Travel could only have occurred in a small area. The solid triangular bar has a cut out area and a small bar is inserted through the corner of the brazed piece which acts as a stop. The pictures make it much easier to understand.

 

Child in a sweet shop…

I have so many lovely microscopes that need work and I am like a child in a sweet shop, I don’t know which to do first! I’m overwhelmed with wonderful choices and I need to make a decision. I would like to get something underway this week. I have a beautiful double pillar microscope which needs a screw making and a bit of a clean but I don’t really think it needs re-lacquering. Do let me know if you agree/disagree with this opinion.  I enjoy re-lacquering more than anything else so I shall probably leave the double pillar for another day when I’m in more of a making screws mood.

I have the Merz which is simple to do and in need of lacquering, I have “the Beast” which is huge and will take many months to do. a selection of small Hartnacks and the like and a rather nice jug handled microscope which has been painted completely black and really needs some love. When I say it has been painted black, I mean completely painted black – even the objectives. Poor little thing.

I think I’ll start with the Merz and then move on to the jug handled microscope. Decision made. If I don’t post pictures of a dismantled microscope tomorrow feel free to come and beat me with a big stick.

This slideshow requires JavaScript.