What is Lino Etching?

Lino etching is the process of using Caustic soda paste (a strong Alkali solution mixed with wallpaper paste) to etch the surface of a linoleum block to create a range of marks.

Caustic soda etches or ‘bites’ into the surface of the lino block to various depths, according to the length of time it remains in contact with the lino block. A wide range of tonal marks can be created, from white (negative) to grey (half tone). Due to the unique nature of this technique, lino etching can be used as both a relief and intaglio process.

Relief - is where a print is taken from the inked top surface of a block.

Intaglio – is where a print is taken from the remaining ink sitting in the recesses of a block/plate after its top surface has been wiped clean.

The lino may also be protected from the caustic etch by the application of a range of mediums which will resist the etching process e.g. parafin wax, stop out varnish, electric tape, Vasaline and more. The resulting areas will print black/grey, when using black ink. In a whole, lino etching is a very painterly technique, capable of producing gestural marks, gradations of tone, and texture. It can also be combined with traditional cutting methods using lino tools.

How does it etch lino?

Caustic soda crystals (Sodium Hydroxide) are generally used as a heavy duty cleaner, especially great at clearing out pipes. Since it’s a strong alkali, it can eat away any organic matter clogging up the plumbing. Hessian lino blocks are made from wood flour and linseed oil making them biodegradable. This also makes them perfect for etching with a caustic soda paste. To neutralize the alkali solution, use vinegar (4-6% acetic acid in water).

Health and Safety

Caustic soda is a strong corrosive alkali that eats away at any organic material. Gloves, apron and goggles/glasses should be always worn. No matter how careful you are with Caustic, there is still a chance it will end up on your tools and the work area, so Ideally you should be working standing up to avoid any unnecessary contact with the tabletop.

In case of contact with the skin (you will feel the sensation of pin pricks and heat on your skin), immediately wash the area with soap and water then apply some vinegar this should cancel out the effects of the alkali solution.

Its best to wear old clothes when doing any printmaking. Long hair should be tied back and sleaves should be down to protect your arms from contact with the caustic solution. Old shoes/boots should be worn not open toe sandals and jewellery should be removed.

Materials

Caustic Soda Crystals – This is mainly used as a drain cleaner and can bought from places like B&Qs, Homebase, and any other home improvement stores.

Wallpaper paste - You can buy this online, or it can be bought in any home improvement store.

Traditional Hessian backed lino - This type of lino is primarily made up of wood flour and linseed oil, making it the perfect surface to etch with caustic soda paste. Easy cut lino and laminated lino will not work as they are not organic based. It can be bought from printmaking specialists.

Newspaper (lots of it) or Silicone mats – This will be used to protect the work surface you will be using and capture any excess soda paste.

Masking tape – Printmakers should always have a couple of these at hand!

Measuring jug

Tablespoon/Tablespoon/dessert spoon - for measuring out ingredients

Glass Jars or plastic round food/Tupperware containers (with lids!) – For mixing and storing the etching solution.

Plastic clay tools and palette knives - Great way to create and control marks with the caustic soda paste.

Plastic/metal decorators’ combs – Another source of mark making.

Plastic handle/Synthetic nail brushes – to help you clean up your lino blocks once they have been etched. It must be synthetic, or the alkali solution will eat away the bristles (it will smell like egg if it does). Avoid wooden handles, they can also be etched by the paste. Any Aluminium wrapped around brushes will also corrode.

Synthetic brushes/plastic handles - A range of different sizes brushes is always good to have for this process. Allowing you to control the amount of caustic paste you apply to the lino block. I buy decorators brushes as they usually come with plastic handles and synthetic bristles. Perfect for the job!

Rollers, Hard or Soft? – Both! This depends entirely on what marks you want to pick up. Usually for relief printing you would use a soft roller, as it gives you a nice even coverage of ink and no roller marks at the edges of the block. Though for some lino etching this could be more of a hindrance, as that much ink could fill in the subtler marks left by the etch. Resulting in you missing out on a lot of detail. So, experiment with your rollers and find out which one does the job best.

Glass inking slabs – Your main work surface for inking your blocks on.

Cad foil/acetate – Used to help with registration when applying more than one colour to a print.

Medium/thick card – for use in registration

Paper

Carbon/Graphite paper – to transfer images to your lino block.

Mixing caustic soda paste

Recipe:

Water: 200ml

Caustic Soda crystals: 3 Dessert spoons

Wallpaper paste: 2.5 Dessert spoons

Please refer to health and safety to make sure you are wearing the appropriate clothing, shoes and protection before handling dangerous chemicals. Caustic Soda gives off fumes and heat when you first mix the solution together, please work in a well-ventilated room and wear a mask. Fumes and heat should dissipate after 15/20mins once the chemical reaction has run its course.

Using a measuring jug pour out 200ml of water into your desired container for the etch solution. Ideally this should be a plastic or glass container which can be sealed airtight with a lid.
Next, measure out 3 level dessert spoons of Caustic soda crystals and pour them into the water - I usually have a container underneath to catch any excess crystals. Caustic soda Crystals react to air quickly causing them to stick together. Which can be a problem when trying to mix a solution together. To avoid this, make sure to put the lid back on the bottle/tub as soon as your done with the crystals.
Finally measure out 2 ½ dessert spoons of wallpaper granules and pour them into the solution. Using the same spoon, begin to gently stir the mixture together. The solution should begin to thicken, and the container will start to heat up. Fumes will be produced during this time so please avoid having your head directly above the solution.
Your caustic soda paste is now ready!

WARNING - Do not put caustic soda crystals in first and then add water. This results in a dangerous chemical reaction!

Note – caustic soda paste can be stored and used for a week before the wallpaper paste in the solution starts to breakdown, becoming a thin solution of Caustic water. Still usable but uncontrollable.