Pinball games from the era we are interested in, those made during the 1950s to the 1970s, were extremely well made. The fact that those still surviving are usually in good structural condition and can be made to look and function well once more is testament to this. Of course, if they have been stored for long periods in less than ideal conditions, they may have deteriorated considerably. A damp environment with large changes in temperature will wreak havoc with cabinet joints, back glasses and playfields. Storing a game with no playfied glass to protect it, orno back door to protect the back glass, in bad conditions, is about the worst thing to do to a machine short of letting it sit immersed in water. Unfortunately, many games have been reduced to parts donors because they have been stored in a garden shed or damp outbuilding.
The cabinets of these old games were a mixture of solid timber and plywood. The later the game, the more the use of plywood was common. The joints were very well made, but the adhesives of the period were not as long lasting as modern ones. Often, those joints need cleaning out and re doing with better adhesive, the cabinets clamped until the glue sets. The base of the cabinet was 1/4" ply, and that sometimes needs replacing. The cabinets are well braced with glued bracing. Most cabinets only need the joints repairing and they are good for several decades more.
The art on the cabinet was a base coat of one colour. There was no primer coat or undercoat. This then had webbing or spatter applied. These random dot or fine line patterns helped to hide the imperfections in the timber, which was not that well prepared before the paint was applied. Then the colour art was applied using brass stencils. Early games usually had three colours, later games had two. The stencils were simply held up against the cabinets and the colours sprayed on. Because the stencils didn't always fit to the cabinet sides well, a certain amount of overspay occurred, making the edges of the stencil colours blurred instead of clean. This is the reason I use stencils to replicate that art. Masking tape would produce clean lines, which would not be as original.
Cabinets up to around 1960 had wooden side rails, lock down bars and frames around the top box. These are referred to as woodrail games, and have a lovely antique appearance. Games up to the mid 1950s also had wooden legs. Few of these early games are offered for sale in the UK, though many still exist in the USA.
Cabinets after the woodrail era were fitted with brushed stainless steel side rails and lock down bars of varying styles. From around 1955, games had metal legs, the early ones were painted in various colours, the later ones were bright plated. The back boxes are usually had no frames and were simply painted. Gottlieb single player games from 1960 to the end of EM production, in 1978, are tapered across the width, from top to bottom. The are referred to as 'wedge heads' because of this. Williams made some games in the early 1960s where the back box tapered, again across the width, from narrow at the top to wider at the base, and these are referred to as 'reverse wedge heads'.
The motor board, the board inside the cabinet which supports the score motor, transformer and various other components, is bolted to slats fitted between the cabinet sides, near the cabinet base. It is usually constructed from plywood. The most it usually needs is a good sanding to clean off years of black dust and lubricant.
The play fields on these games are made of plywood. It must have been of the highest quality, as it is usually still flat and solid, if the game has been well cared for. Earlier games seem to have playfields which have stood the test of time better than the later games from the 1970s, with less graining (known as planking), suggesting it was better quality. The ply wood was sealed all round to stop damage from damp, before the art was applied. Plastic inserts were glued in to holes in the plywood, to allow the light from lamps positioned below them to shine through. The art was applied over a base coat of white to give the colours more depth. This art included thin black lines around the inserts and joints in the coloured areas. They are called key lines. The whole lot was then coated with a protective lacquer. All these layers were applied using the screen printing process, and the medium was ink, not paint, which it is often mistaken for. The lacquer is very hard wearing and has usually done the job of protecting the art well. Where small areas are worn through, usually around pop bumpers, where the ball lands from a kick out hole, or in front of a slingshot, a touch up can be successfully done. It takes time and effort to match the colours and texture, but the result can be made acceptable. Those areas can then be further protected by the application of a clear mylar ring, spot or similar. Really bad playfield wear can be repaired by completely re painting the play field, but it is a time consuming and expensive process. Because the base is wood, water is the enemy and should never be used to clean the play field. Storage in damp envoironments is also to be avoided. Coats of paste wax polish over the clear lacquer coat are the best way to protect the playfield art. A shiny new ball is also recommended, as a rusted or pitted ball will quickly wear through the protective lacquer.
The back glass art is very delicate. Most of the back glasses on these old EM games had the art applied via screen printing, again using ink, on to the glass, or occasionally on to Perspex (this was sometimes used for export games). The completed art then had a white layer applied, to spread the light from lamps used to back light certain areas. Lastly, an opaque mask was applied to stop any light shining through where it was not wanted. The ink can be in a very delicate condition after several decades, and a back glass must be handled with great care to avoid any damage.
It appears that the rate at which the inks and glass expand and contract differ. Where glasses have been exposed to large changes in temperature, from being stored badly, or due to the the heat from lamps used to back light the art and score reels, hairline cracks can appear in the ink over time. The ink often also de laminates from the glass, small flakes peeling away and falling off completely. This can sometimes lead to large areas of the back glass art either thinned or completely missing. This seems to be a far less common problem on the Perspex glasses. Repairing this damage involves applying a stabilising coat of clear lacquer (Krylon Triple Thick Crystal Clear Glaze is commonly used). Then touching in the affected areas to repair the damage. This is easy enough to do in any areas where the light proof mask has been applied. It is far more difficult to repair areas which are seen as lit up. Results can vary from very good to just acceptable. Reproduction glasses are available, at high cost, for some games, but for many, none are available. New methods of making replacement glasses are constantly appearing, so often a replacement can be made without using the silk screen method. None of these are quite the same as the original, but are good enough to be acceptable, especially in preference to a badly damaged glass.