With the background prepared, the next step is to make a good mix. It pays to mix your plaster close to the work site, as it can be a messy job. Cover the floor with plastic dust sheets or old newspapers, and remember to wipe your feet when leaving the room.

Plaster that is mixed to the correct consistency will be easier to apply. Use a plastic bucket to measure the cement, lime and sand or plaster accurately. For large quantities of plaster, simply multiply the number of bucket measures. For small quantities, just use half-bucket measures or less.

Old, hard gypsum plaster stuck to your equipment can shorten the setting time and reduce the strength of the newly mixed plaster. Do not try to rework plaster that has begun to set by adding more water: discard it and make a fresh batch. Mix only as much plaster as you will need. For larger areas, mix as much as you can apply in about 20 minutes — judge this by practice.

Bonding agents modify the suction of the background or improve the adhesion of the plaster. When you are using a bonding agent, do not apply the base-coat plaster any thicker than 9mm (3/ain) at a time. If you need to build up the thickness, scratch the surface to provide an extra key and allow at least 24 hours between coats.

Bonding agents can be mixed with plaster or sand and cement to fill cracks. Brush away any loose particles and then apply a solution of 1 part agent :3 to 5 parts water with a brush.

Mix the plaster or sand and cement with 1 part bonding agent :3 parts water to a stiff mix. Apply the filler with a trowel, pressing it well into the crack.

Wash tools and brushes thoroughly in clean water. It may be necessary to rinse out the brushes as the work progresses on a large job.

Mix undercoat plasters on a mortar board (see opposite). For sanded plasters, measure out each of the materials and thoroughly dry-mix them with a shovel, or a trowel for small quantities. Make a well in the heaped plaster and pour in some clean water. Turn in the plaster, adding water to produce a thick, creamy consistency.

Just add water to premixed gypsum plasters (which already contain an aggregate). Mix them on the board in the same way. Always wash down the board after you have finished using it.

Mix finish plaster in a clean plastic bucket. Pour not more than 2 litres (4 pints) of water into the bucket, then sprinkle the plaster into the water and stir it with a stout length of wood until it reaches a thick, creamy consistency. Tip the plaster out on to a clean, damp mortar board ready for use. Wash the bucket out with clean water before the plaster sets in it.

You can mix small quantities of premixed plaster in a bucket. Pour the plaster into the water and stir to a creamy consistency; 1kg (2lb 4oz) of plaster will need about 0.75 of a litre (11/2 pints) of water.

Pour out a small heap of cellulose filler on to a flat board or tile. Scrape a hollow in the centre with your filling knife and pour in water. Gradually drag the powder into the centre until it absorbs all the water, then stir the mix to a creamy thickness; if it seems too runny add a little more powder. Begin to fill deep holes and cracks with a stiff mix, but finish off with creamy filler.