Glossary - S
Sagging (curtaining)
Usually occurs on vertical surfaces where paint has been too thickly and unevenly applied resulting in 'horizontal runs' with a thick lower edge.
Sags and runs on new paintwork
This is usually caused by uneven paint application on broad, flat surfaces, or by over-applying on mouldings or rough-contoured surfaces. Also, failing to join up 'wet edges' before they have set can cause excessive film thickness, resulting in sagging and running. When the paint film is thoroughly dry rub down the sags/runs using wet and dry abrasive paper (or waterproof silicon carbide) together with warm water and detergent. To prevent sags/runs when painting broad, flat areas, work systematically and cross-brush each section into the next; finally using vertical strokes to gently lay off along the length of the surface.
Salt staining on plywood
Salt staining can appear on wood stained exterior grade plywood, especially on eaves and soffits. Salts are contained in the adhesive used to bond the layers of plywood together. Because wood stains are very permeable, they can bring these salts to the surface of the wood. Rainwater will normally remove these salty deposits, except in sheltered areas such as soffits and eaves. The only way to remove these deposits is to wash them down until they no longer appear. For further guidance, see BS 6150 Section 26.
Sand blasting
Grit and sand-blasting are processes used in the preparation and cleaning of steel to remove millscale and corrosion products. They are highly specialised processes.
Sanding
The use of an abrasive to level a surface prior to painting. The more common term used by painters is 'rubbing down'.
Saponification
In the paint trade it refers to the chemical attack of the paint media by alkali usually from the substrate. e.g. the alkali reacts with the oil content of an oil based paint and turns it into a soap, resulting in disintegration of the paint. Oil based paints are very susceptible to saponification whereas emulsion paints generally have good resistance to alkali attack.
Sarking
A bituminous underlay placed beneath tiles or slates.
Sash window
A window in which the opening parts slide up and down in the frame.
Screed
A band of plaster or mortar laid on the surface of the wall as a guide to the thickness or level of the plaster to be applied. Therefore also used for the coat itself and for the levelling coat on flooring.
Scumbling
A technique in painting where by the final coat is patterned or partly removed to expose the undercoat or ground in order to obtain colour variety or movement.
Section
Any outline drawing showing the shape of a moulding structure or object as it would appear if cut along a line and viewed at right-angles to the cut; particularly refers to the drawing of a building prepared in this way as opposed to a plan or elevation.
Seediness
The appearance of very small particles in the dried paint film.
Semi-gloss
An intermediate level of gloss between a 'full gloss' and an 'eggshell' finish.
Set
The condition of a paint coating when it has ceased to flow.
Setting coat
The final coat in a plastering process usually consisting of about one-eighth of an inch of fine plaster.
Settling
The deposition of the solid particles of a paint to the bottom of the container.
Sharp coat
Strictly speaking it is an application of a white lead/linseed oil paint liberally thinned with white spirit or turpentine. By dint of, this 'sharp' has come to be used for any thin and/or quick drying paint.
Sheariness
A variation of sheen or gloss in a dried paint coating producing an uneven patchy appearance.
Sheary
An irregularity in gloss or sheen on a surface.
Sheen
The degree in gloss of a low gloss or matt type finish.
Shop priming
Factory application of primers to wood or metal, etc.
Short oil
The term used to describe a varnish or paint medium which contains a low proportion of oil in relation to its resin content.
Shot blasting
See 'sand blasting'.
Shrivelling
The overall fine-surface wrinkling of a glossy paint film.
Shuttering
The general term for temporary supporting structures for concrete while it is setting. Also from work.
Silk or satin finish
A finish with a low to medium degree of sheen or gloss.
Sill
The lowest timber or member in a structure frame or opening. The timber or stone at the bottom of a door or window opening.
Sinkage
Loss of gloss or colour due to the absorption of the medium by the undercoat or surface beneath.
Sirapite
A common type of hardwall plaster. It may or may not be mixed with lime.
Size
A mixture of glue and water.
Skirting
A board or member at the base of a wall, probably a corruption of 'wainscotting'.
Sleepiness
Condition of a recently-dried glossy paint film which has lost its initial gloss slightly.
Sleepy
The description of a recently applied gloss paint which has a 'hazy' appearance or lower than normal gloss.
Slurry
A thin paste produced by mixing some materials, especially Portland cement with water.
Smudge
A term used for a mixture of paint with remainders of all types and colours.
Soffit
The underside of a staircase or of the head of an opening such as a door window or arch. Hence also used for the underface of a beam or for any small ceiling at a different level to a main ceiling.
Softwood timber
Timber from trees with needle shaped leaves mostly evergreen e.g. conifer. This term has no relationship to the actual hardness of the wood. This timber is most commonly used in house construction.
Soil pipe
A vertical lead or cast iron pipe conveying waste matter from WCs, etc. to the drains. Unlike a rainwater pipe it will have sealed joints and is usually continued above eaves level to form a ventilator.
Solvent
A liquid component used in paint to bring it to a suitable consistency for use and which evaporates from the paint after application. Also a liquid which will dissolve dried paint, e.g. cellulose thinners on cellulose; chlorinated rubber paint thinners on chlorinated rubber paint.
Span
The horizontal distance between the supports of an arch roof or beam, etc.
Spandrel
The triangular area formed between an arch and the horizontal member it supports, hence 'spandrel panel' - the shaped panel formed in the spandrel.
Spattering
Droplets of paint that spin or mist off the roller as paint is being applied.
Spot priming
The priming of localised bare timber surfaces when 'bringing forward' prior to stopping up and/or painting.
Spraying
Application of paint by a spray gun. Two types of spray are available: 'conventional' which is operated by compressed air, and 'airless' operated by hydraulically compressing the paint.
Spreading
The action of applying paint by brush in a uniform coat over a surface; colouring bare wood by means of a dye or stain; discolouration of a paint film.
Spreading rate
The area which a given quantity of paint will cover, e.g. the spreading rate of a particular paint may be quoted as '15m2 per litre on smooth surfaces of average porosity'.
Stanchion
A prop or support to a roof ceiling or beam. Especially refers to cast iron or rolled steel member used as a supporting column.
Starved
See 'hungry'
Sterilise
The treatment of surfaces to kill off organic growth such as mould or algae prior to painting.
Stile
The vertical part of any framing into which the horizontal rails are fixed by mortices and tenons.
Stipple
A method of evening out a coat of paint by dabbing or lightly beating out the surface immediately after application with a special brush (stippler). Hence the texture or appearance of a paint surface so treated.
Stopping
The action of filling up joints, deep imperfections or holes in a surface before painting.
Stoving
The process of drying and hardening a paint coating by heating in an oven or other apparatus.
Stretcher
A stone or brick laid so that its length is in the line of the face of the wall. Opposite to 'header'.
String course
A projecting course of stone or brick continued horizontally along the face of a wall.
Stringing
The supporting board of a staircase farthest from the wall.
Stripping
The removal of old paint or paper.
Stucco
A smooth-surfaced cement or rendering applied to external walls, especially if it resembles stone.
Substrate
The surface or composition of the structure which is to be painted.
Synthetics
Term loosely applied to paints containing a proportion of, or based entirely upon a synthetic resin. The use of the term should be avoided as it is not sufficiently precise.
Saponification of oil-based paints on plaster
Saponification occurs when oil-based paints are softened and liquefied by the alkali in plaster when moisture is present. Materials containing Portland cement or lime are strongly alkaline; gypsum plasters are usually not, but can become alkaline if gauged with lime or if it is brought forward from the backing during the drying phase. For these reasons, never use oil (solvent) based paints on plaster or masonry surfaces until they are completely dry in depth, then prime the surfaces with Dulux Alkali Resisting Primer. Where saponification has occurred, completely remove the defective coating, wash down the surface and rinse with clean water. Allow to dry then prime with Dulux Alkali Resisting Primer.
Seediness
There's really only one solution to this one: thoroughly clean down the surface to remove all dirt, grease and surface contaminants. Rub down with a suitable abrasive, dust off, and re-paint the affected area.
Sheariness
This variation of sheen or gloss in dried paint is known as 'sheariness' and is often seen in brushed emulsion paints when viewed from a shallow angle. To correct this condition, thoroughly clean down the surfaces to remove all dirt, grease and surface contaminants. The scrape back all areas of poorly adhering or defective coatings to a firm edge, rub down to 'feather' broken edges, dust off and repaint.
Shrivelling (or rivelling) on new paintwork
Known as 'shrivelling' or 'rivelling', this wrinkling effect can occur when paint dries too quickly, forming a surface skin before the paint underneath can dry properly. Overcoating a previous undercoat or gloss to soon can also cause shrivelling, as can applying oil-based coatings at low temperatures. Before attempting to smooth out the wrinkles, allow the surface to dry and harden, then rub down using wet and dry abrasive paper with warm water and detergent. Rinse thoroughly with clean water and allow to dry before repainting.
Sinkage
When the gloss or colour of the coating has been absorbed by the undercoat or the surface beneath the coating, first thoroughly clean down the surfaces to remove all dirt, grease and surface contaminants. Then rub down with a suitable abrasive and dust off before priming all over with a suitable primer for the finishing system.
Sleepiness
Apply another coat of paint, after first cleaning down the surfaces to remove all dirt, grease and surface contaminants. Then rub down with a suitable abrasive, dust off and repaint.
Slow drying of gloss/varnish on new paintwork
With solvent-based paints, it's usually surface contamination as the result of a poorly prepared surface. Water-based paints can be slow to dry in damp, cold conditions, or when applied to timbers that are oily by nature, such as teak. Wet solvent-based paint may be removed using cloths soaked in white spirit. If this is unsuccessful, completely remove the coating using a hot air gun or a suitable chemical-based remover. To remove slow-drying water-based paints, simply wash off with warm water and detergent solution.
Staining/discolouration of paint on masonry
There are a number of principal causes:
1) Certain types of sand used in the construction or rendering of a building can cause staining, as can certain kinds of brick hollow clay pots or clinker blocks containing soluble salts. Pieces of ferrous metal or iron stone embedded in the material can rust and discolour when the surface is painted. These problems can be treated by sealing the affected areas with Dulux Alkali Resisting Primer when the surface is completely dry.
2) 'Rust' staining can occur where old nails are left in the substrate, or a wire brush has been used to prepare the surface. In this case, prime locally with Dulux Metal Primer prior to painting.
3) Steel reinforcing in concrete may be too close to the surface and cause rusting. The only effective way to resolve this problem is to get back to the metal itself and treat the cause of the rust.
Staining/discolouration of paint on plaster
Past water leaks or burst water pipes can cause staining. Before repainting, ensure that the leak has stopped and the surface is thoroughly dry, then spot prime the affected area with Dulux Alkali Resisting Primer.
2) Heavy deposits of tar from cigarette smoke and around the chimney breast of open fires are common causes of staining, especially on water-based emulsion paints. To prepare, wash the surface thoroughly with detergent solution and rinse frequently with clean water. Allow to dry, then prime with Dulux Alkali Resisting Primer. If using water-based paints, allow a few days for the oil deposits of the primer to disappear, otherwise cissing may be a problem.
3) Conventional solvent-based finishes such as gloss can discolour with age, particularly in areas sheltered from natural daylight. Prior to repainting, wash the surface with a detergent solution, rinse with clean water and allow to dry. It may be more advisable
to use a water-based coating for a low light area.
Staining/discolouration of paint on wood
There are different solutions for each of these problems.
1) Staining caused by rust from old nails should be rubbed down to remove the rust, then prime any exposed metal with Dulux Metal Primer or Dulux Q.D. Metal Primer before painting.
2) Resin bleeding from knots in wood should first be removed with white spirit. Then seal the knots with two coats of Dulux White Knotting Solution and repaint.
3) All solvent-based paints such as gloss will discolour or yellow with age. To treat, wash the surface thoroughly with detergent solution, rinse with clean water and allow to dry before repainting. If the wood appears to be dirty, particularly around glazing rebates, it may be affected by fungal growth. Clean the surface thoroughly and treat with domestic bleach, or apply a coat of Aluminium Primer, before painting.
Stickiness
There's only one thing for it. Completely remove all existing material and carefully clean down the surfaces. Allow to dry, then reapply coating.