Cleaning and preparing glass is possibly one of the most important stages in any photographic process where the glass is used for a negative or for printing.

I buy new glass from supplers who frame pictures. I ask them for all off-cuts in any size and often they will give these for nothng or for a very small sum. New plates of glass which are around 1.2 meters by 1  meter cost from 22 euro per square meter. The best supply I have found is buying the picture frames from bargain stores. These cost from 99 cents for half plate size to a few euro for 40 x 50 cm. This is usully all 2mm glass, some is 1.5 mm.

I also use old  glass from picture frames or windows. Some very old glass was manufactured differently from today and has an interesting “character”I cut glass with a simple “Toyo” glass cutter and make a lubrication oil from white spirit. I found a simple jig to set the glass size and can cut plates all to fit my holders or suit the print. after cutting –

1 – The first step is to file off all the edges, I use an abrasive stone, the type used for sharpening chisels.

2 – The second step is to make sure the cut glass fits the plate holder or is correct size for the printing process.

3 – The third step is to carefully inspect the surface for scratches, I reject any which are damaged.

4 – I clip a small piece of plastic used for filing papers on the top edge of the glass. This prevents two pieces of glass contacting and getting stuck together. This is really irritating if the glass is wet and makes sure when I am cleaning the glass sheets keep separated in the washing baths.

 

Cleaning

At all times I wear gloves, a heavy duty apron and safety glasses

1- I put the sheets of cut glass, with the plastic clip to keep them separated into a bath of hydrochloric acid (from 20 to 30 percent) and leave overnight. I either do this in a fume cabinet or outside in a safe place away from people or animals.

2 – I take each sheet from the acid, rinse under cold water and put it into a large container of clean water.

3  – I take the container to a work table – take each sheet and rub for at least 20 seconds (longer for big plates) with disposable paper towel which has a little diatomaceous earth and cheap alcohol (80 percent is fine).

4 – When my wife is not looking I put the plates , usually abut 20 or 30, into the dishwasher and run it.

5 – I take the glass from the dishwasher, take them to a work bench and wipe carefully with isopropyl alcohol. I clip each plate with the plastic separation piece (cleaned) and mark the back top left corner with an indelible marker pen – I use a simple number code to tell me the date I did this.

Preparing the glass for printing.

I take each plate and pour on a coating of amino silane (from 3M) as if I was coating the plate for wet plate collodion. I put the plates in a plate rack and leave a few hours to dry

I then coat the glass plate with a gelatine size, (this is around 38 degrees C) again in the same way as for wet plate collodion, – I pre-heat each plate to around 32 degrees C on a commercial dinner plate warmer. I leave to air dry overnight and then the glass is ready for printing.

I prefer to use the glass I have prepared within a couple of days, but I have successfully used plates prepared several weeks earlier.

The gelatine size is a  solution of 250 bloom gelatine with chrome alum added. The formula I use works for me. I found it in The book – “Carbon Transfer Printing” written by Sandy King, Don Nelson and John Lockhart (ISBN; 978-0-429-42519-6) – page 45