I love this technique, but please be aware that Caustic Soda is highly toxic and corrosive, and will not only etch your lino but also, given the chance, skin, flooring, painted or varnished surfaces and textiles.
So, I wear thick rubber gloves, an apron and eye protection. I protect surfaces with newspaper, open windows or work outside.
The mix can be applied straight onto the lino for a very free and painterly effect, though I usually ‘stop-out’ areas which I dont want to etch. I paint on a thick black stop-out normally used in the etching process, made by Charbonnel called Lamour Black Covering Varnish, sometimes scratching back into it with a sharp knife. Drawing with candle wax or waxy pastels/crayon will also work though the caustic soda will eat through anything not applied thickly enough. It always eats through in some places but that’s part of the excitement of this very unpredictable, textural method.
Once the stop-out is dry, I put on gloves, eye protection and apron, put newspaper down. Taking a glass jam jar, I fill it about a third full of water, sprinkle in a couple of teaspoons of dry wallpaper paste flakes into the water and mix. Leave for 3 or 4 minutes until it thickens. Now I carefully pour in about 2 teaspoons* of caustic soda granules and stir with a wooden stick.
*I dont use anything metal in this process as the caustic soda reacts with many metals. Always start with the water and add the caustic soda to it. Read the instructions on the back of your caustic soda container – it will give you the safety procedure.
The mixture will heat up and give off fumes.
If any gets on your skin then it really burns. Wash immediately with lots and lots of water. Vinegar will also apparently neutralise the process.
Using the stick I apply the now thick gloopy mixture to my lino. Wait 2o-30 mins.
Washing off the plate under a hot tap using a toothbrush to clean the surface thoroughly, I take care not to splash the mixture back at myself or at the surroundings. Pat dry with newspaper. I then wash any unwanted mixture down the plug hole with copius amounts of hot water.
The depth of etch will vary depending somewhat on the strength of the mix, the age/type of your lino, and the temperature. A test strip using different resist methods, and timings helps to establish what might happen.
As you can see, 5 mins hardly etches at all, but does give an all over texture, and 60 mins bites very deeply so there is much more contrast.
Remove your stop-out, the black varnish comes off with white spirit. Candle wax can mostly be scraped off and the remainder melted off with layers of brown paper and a just warm iron
Print plate as per usual. Repeat for reduction print.
Any large expanse of etched lino will still pick up ink as the paper is pushed down into the etched area, especially when hand printing using a barren, but this can be used for good effect. You can deliberately push the paper down onto the plate to pick up ink.
