Patination

practical guide by G.E.Knell

Preparation of the work.

For the successful colouring of bronze surfaces all grease, oil, finger marks, can be cleaned using Oxalic acid and rinsed with cold water, or scrubbing using fine sand and water then rinsing off any residual sand.

Utensils

Utensils used for patination should be scrupulously clean. Pour out the colouring solution into a plastic or glass container, (just enough to do the job in hand) when the colouring is finished do not pour the remaining solution back into the bottle, throw it away, as it will probably be contaminated with impurities and will affect future work.

Application

This is the single most important aspect in the art of patination. Consistency in the use of your brush technique and heat if used will ensure that the resultant colour will be as near as possible to the patine that you are aiming for. With some chemicals it is necessary to use heat, and some are best used cold and applied to a cold surface. The main requirements of a patinator is extreme patience and an artistic flare, with a common-sense approach when using dangerous chemicals, i.e, work in a well vented area, and keep all chemicals not in use, locked in a suitable cupboard, and wear protective clothing.

Apply the chemical solution to the work with a brush, using a stippling action, keep this up until the entire surface has been covered, dipping the brush into the solution as required, never allow the work to become so wet that the solution runs down and causes streaks to appear which are very difficult to eliminate, When the work has been completely covered carry on stippling with a dry brush, this will give an even patine.however other brush techniques can be used to good effect, you may need to apply more than one coat of the solution.

When using a cold application it should be done in a cool area and not in direct sunlight or rapid drying will occur, and you will have no control in the application.

Patinating using copper nitrate, ferric nitrate and the like can be carried out in almost all  conditions, as extremes of heat are used. With this technique cleanliness still applies The flame is used to heat up the surface of the metal and chemical is applied at the same time until the desired colour is achieved. 

 Waxing

Generally the work is not waxed until the colour has had time to rest, say overnight. There are many waxes that can be used all claiming to be the best, however the patinator usually discovers his own type of wax, the important thing here is that the wax used should be durable.

Waxes can be purchased from good quality hardware shops, a popular wax is a white prepared beeswax, which is in a paste form, also Johnsons traffic wax is a useful one to use, especially on bronze maintenance work. Pure bleached beeswax which comes in blocks is a very good wax to use, but it requires a technique in it’s application, a brush is used and dipped in a solvent, (white spirit being a very popular one) the brush is then rubbed into the beeswax block until sufficient wax has been dissolved and picked up on the brush and applied to the bronze using a gentle stippling action, avoid applying to much and making it impossible to polish the work, the thinnest coat of wax is what is required, this can be built up over a number of coats to give a deep gloss to the work. Some of the fresh light green patina can be spoiled by applying wax, in this case a white bees wax applied with petrol as the solvent can be used. A very dangerous method and should be avoided where possible. On old mature patine the normal waxes can be used. In most cases waxing can have the effect of darkening the colour, often to the benefit of the final appearance of the bronze.

Other waxes that contain carnuber wax, paraffin wax and beeswax mixed with a solvent are very effective, these waxes are often mixed by craftsmen to suit there own techniques.

For some applications it may be necessary to mix coloured dye in with the wax to achieve the desired effect on the bronze surface, however dyes do eventually bleach out, especially on external works.