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* Building the LMS Stanier Black 5

* Build GWR dia. AA11 "Toad" from a kit

* Machining Steel Wheels

Decay….

Most of us are familiar with “weathering” as the concept of covering locos and rolling stock with rust and muck. What I am going to deal with here is the WHY and HOW it happens.

Rusting.

Rusting only affects steel where there are both liquid water and an oxidiser present. However it is possible to prevent rust by heat treatment to produce an oxide layer thus giving the “Russian Iron” or “Blued Steel”. These were both common of US built rolling stock and locos. Other methods such as Galvanising with Zinc or molten Tin plating produce differing looks to the rusting process. Once the Zinc layer has been breached the edges will take on a slight white tinge and the Zinc forms Zinc BiCarbonate and this washes off in the rain. Tin plate is effective but has problems in low temperatures where it will “scab” and fall off in large pieces. This is due to the Tin changing state to another allotrope. Once this happens the Tin will not re-connect with the parent steel and then it begins to rust and the layer of paint is forced off. Thus the seemingly large areas of rust in otherwise pristine paintwork.

Verdigris.

The nice pretty green colour covering civic building is caused by the slow oxidation of Copper. To hasten the process sometimes the Copper is heated with a blow torch until it forms black Copper II Oxide. Rain and atmospheric CO2 then attack the layer of Oxide and converts it to the pretty Copper II Carbonate. Depending on the roofer the sheets of Copper will have been rivetted together or Lead soldered. If the latter then distinct grey solder lines will show -but the roof has a greater lifespan.

Things growing out of Walls.

This may seem to be the most puzzling thing but is so common nowadays on old buildings that no-one gives it a second thought. The reason is both simple and complex. Modern brick walls are based on bricks with “frogs” or other forms of mortar grip such as vertical holes in them. Most brickies today will use a portland cement based mortar. This was not always the case. Before the first World War and for some time afterwards the most common mortar was “lime putty”. This was a simple mixture of sand and slaked lime mixed with some water. This could take days to set. To aid this a number of wooden pegs would be inserted into the layer of mortar and then removed. These left “weeping holes” for both water to escape and CO2 to enter and turn the slaked lime into solid limestone. The “weeping holes” were supposed to be covered up by the “pointing” that finished the walls. However once the pointing fell out there were nice holes already waiting in the wall. Added to this it was quite common to fill the gaps between the walls with “cob”, AKA mud!

As the pointing would be mixed in large quantities It is common to find that whole areas of pointing will fall out whilst others “mysteriously” still stay stuck to the bricks. This is due to lazy apprentices mixing too much sand into the mortar rather than mess with the chokingly unpleasant slaked lime…

What sort of things are likely to grow out of a wall? Well due to the very alkaline environment the most common answer are Buddlea and members of the Plum family! My Brother in Law is a builder who specialises in restoration work and the first thing he does is examine the “trees”… Sloes and Bullaces are the most common due to bird droppings, whilst Buddlea is more wind blown. With “Plum Infestation” The only cure is to hack out the infected rooted part of the wall, clean off the bricks and then re-brick it with the cleaned bricks. This leaves a typical triangular scar of new mortar with old bricks. These will be found towards the top of walls. “Buddlea Infestation” is the stuff of nightmares. The only solution is to rip out the wall and then relay with new bricks and mortar. The old bricks have to be baked to destroy the seeds.

Derelict land.

Depending on the original inhabitants of the area the local decay can follow two tracks.

A former railway location will favour Silver Birch and Maples of various types. The ground cover will be a good mix but will normally contain Teasels and Gorse. This is because the limestone ballast will slowly remove the acidity of the soils. Ironically this is the perfect environment for natural orchids to bloom as can be seen in the ash tips(!)

The other track is one of industrial decay. Here rusting steel and shattered brickwork with lime putty will produce a very limited local plant life. Ground cover may be absent due to the relative infertility of the soils and there may be a few “weed trees” around.

Asbestos Surfaces.

During the late 19th and early 20th century Corrugated Asbestos was a common roofing material. This was a simple mix of chopped asbestos fibres, portland cement and plaster of paris. This dough was squeezed out between heated iron rollers and then put to one side. The plaster of paris held the sheets rigid whilst the cement hardened over the next couple of days. The mix served very well until about 30 years after the Second World War. Thereafter the known problems with asbestos began…

New asbestos has, (I am informed), a slight greenish grey colour which the sun and rain convert to a pale grey as the portland cement cures. It would appear that the asbestos surface changes colour to a pale green. This is a half truth, the pale green colour is due to the combination of the lichen that loves this surface and mosses in natural crevices produced. Moss cannot grow without the area being in sunlight as it is a plant which requires quite a lot of water. Lichen is a fungus and does not require light as it is a symbiotic organism between algae and cyanobacteria. Thus it can live in direct sunlight and dark -provided it has plenty of water!

Graffiti.

This is actually quite datable. The origins of Graffiti are not as would be thought -the USA but France. It was in the form of patriotic slogans painted on panels that held apart the walls of the trenches of WW1. However it was the invention of the aerosol spray can that gave US “artists” their quantum leap. Beforehand a brush and bucket of paint was all they had -both of which could be traced by the police. An aerosol can had nothing (except probably fingerprints). Thus wide angular sweeps of colour rather than simple lines of paint brush strokes became the norm from about 1965 onwards

Over the course of years some “tags” have arisen that now make no sense to modern eyes.

GOD save the King from Baldwin. Early 30’s.

Maefeking has been relieved. Boer War.

Kilroy was here. WW2.

LMS -hell of a mess. Late 20’s.

Y2K. Late 90’s

Dyslexia rules K.O. 70's and 80's

The paint that the Graffiti was made with will of course itself decay. Paints made in the Edwardian era will be metal based or lime wash. These will be quite rapidly removed by the weather, but will stain brick work with a “shadow” image. Modern based paints using acrylics tend to scab in cold weather.

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Page last modified on April 02, 2018, at 12:48 PM