Abrasive fleece#Backing & construction: A synthetic fleece with grain embedded in it. It follows edges and profiles and dulls the surface rather than removing material – for spots paper cannot reach.See also: Blending in · Flash rust · MattingRead more: Non-woven abrasive or sandpaper? · What grit before painting? · What grit for clear coat?
Adhesion promoter#Work steps: A very thin intermediate layer that lets primer surfacer or paint hold on smooth, hard-to-wet surfaces – above all plastic and bare aluminium. It goes onto the keyed, cleaned surface.Read more: Sanding and painting plastic · What grit before painting?
Aluminium oxide (corundum)#Grain & grit: The most common abrasive grain: tough, slow to break down and suited to wood, metal, body filler and paint. White fused alumina is the purer, sharper version.See also: Ceramic grainRead more: Our abrasives range · Aluminium oxide, silicon carbide, ceramic: which abrasive grain for what?

B

Backing pad#Sanders & accessories: The round plate of a random orbital sander that the disc attaches to with hook-and-loop. Diameter, hole pattern and hardness (soft, medium, hard) have to match the disc and the job.See also: Interface padRead more: Which backing pad fits? · Mesh sanding discs vs. regular sandpaper · Sandpaper for random orbital sanders
Belt sander#Sanders & accessories: A sander with a continuous sanding belt for fast, straight stock removal on large wooden surfaces. It sands in one direction and bites hard – for paint and body filler a random orbital sander is the better choice.Read more: Which sander for which job? · Sandpaper for orbital sanders: size, grit and how it differs from a random orbital sander
Blending in#Work steps: Fading a paint repair softly into the surrounding original paint instead of painting the whole panel. The blend zone is flatted with P800 to P1000 wet or fine non-woven abrasive so the new paint adheres and no edge remains visible.Read more: Which grit for car paint?
Bond (resin bond)#Grain & grit: The resin or glue layer that holds the grain on the backing. It helps decide how long the grain stays sharp and whether the abrasive can be used wet.Read more: Wet or dry sanding?

C

CAMI (grit)#Grain & grit: The US grit standard, usually just given as “grit”. In the fine range CAMI and FEPA numbers drift well apart – 400 grit is not P400.Read more: Converting P grades and US grit
Ceramic grain#Grain & grit: Sintered aluminium oxide with a very fine microstructure: under pressure only tiny particles break off, so the grain stays sharp for a long time. For high contact pressure and hard metals such as stainless steel.Read more: Sanding stainless steel and aluminium · Aluminium oxide, silicon carbide, ceramic: which abrasive grain for what?
Clogging (loading)#Sanding defects: Sanding dust, resin or soft metal fills the gaps between the grains – the disc turns shiny, barely cuts and leaves scratches. Dust extraction, less pressure, a stearate coating and mesh abrasives all help against clogging.See also: Dry sanding · Service life · Wet sandingRead more: When is a sanding disc worn out? · Wet or dry sanding?
Coating density (open / closed coat)#Grain & grit: How densely the grain covers the backing. An open coat clogs less (wood, body filler), a closed coat cuts more evenly (metal, paint).See also: Service lifeRead more: Restoring headlights: which grit?

D

Deep scratches#Sanding defects: The scratches every grit leaves behind. The next grit has to remove them completely – which is why you never more than double the grit number per step.See also: Clogging (loading) · Grit jump · Grit sequence · Primer surfacerRead more: What grit sandpaper for car paint? · What grit for sanding body filler?
Delta sander#Sanders & accessories: A finishing sander with an iron-shaped triangular pad – for corners, window frames, glazing bars and narrow profiles a round pad cannot reach.Read more: Which sander for which job? · Sandpaper for orbital sanders: size, grit and how it differs from a random orbital sander
Dry sanding#Work steps: Sanding without water – the norm with a power sander. To stop the abrasive clogging and the dust hanging in the air, it needs dust extraction.Read more: Wet or dry sanding?
Dust extraction#Sanders & accessories: Sanding dust is drawn through the holes in the abrasive and pad into an extractor or dust bag. That protects your lungs, keeps the surface clean and extends service life because the grain clogs less.See also: Clogging (loading) · Dry sandingRead more: Sanding dust: extraction and masks · What grit sandpaper for car paint? · What grit before painting?
Dust nib#Sanding defects: A speck of dust that landed in the wet paint during spraying. Once cured, sand it off locally with P1500 to P2000 wet and polish the spot.See also: Intermediate sandingRead more: Which grit for clear coat?

F

FEPA / P-grade#Grain & grit: The European grit standard, recognisable by the P in front of the number (P80, P240). The higher the number, the finer the grain.See also: CAMI (grit)Read more: Grit guide · P240 or 240 grit? Converting grit scales
Film backing#Backing & construction: A plastic film instead of paper as the backing: tear-resistant, perfectly flat and waterproof. The grain sits evenly and leaves a particularly fine scratch pattern – typical for paint and finish sanding.Read more: Mesh sanding discs vs. regular sandpaper · Sandpaper for random orbital sanders
Flash rust#Sanding defects: A thin layer of surface rust that forms on bare steel within hours – and on stainless steel or aluminium contaminated with steel particles. Remove it with P80 to P120 or non-woven abrasive and prime the surface promptly.Read more: Sanding metal: rust and welds · What grit before painting? · Wet or dry sanding?

G

Grain raising#Work steps: Wiping sanded wood with a damp cloth, letting it dry and going over it once more with the last grit. The raised fibres are gone before a water-based finish or stain can lift them.Read more: Sanding wood before oil or varnish
Grit jump#Grain & grit: The step from one grit to the next, for example from P120 to P180. If it is too big, the finer grit no longer removes the scratches of the coarser one – rule of thumb: at most double the number.Read more: Grit guide
Grit sequence#Grain & grit: The order of grits from coarse to fine, for example P80 → P120 → P180 → P240. Each step removes the scratches of the one before – skip too far and they show up later under paint or oil.Read more: Grit chart · Hand sanding: with a block, in strokes, criss-cross · Sanding a wooden staircase: treads, nosings, corners
Guide coat (control powder)#Sanders & accessories: A fine black powder applied before sanding. Wherever it is still visible afterwards, there is a low spot or an area you have missed.Read more: What grit sandpaper for car paint? · What grit for sanding body filler?

H

Hand sanding block#Sanders & accessories: A firm block that sandpaper is clamped or hook-and-looped onto. It spreads the pressure evenly so the surface stays flat instead of following your fingers.Read more: Sanding by hand: the sanding block
Heat tint (temper colours)#Sanding defects: Blue, golden or brown discolouration on stainless and mild steel when the metal gets too hot during sanding. Sand in short passes with little pressure and let the spot cool down.Read more: Sanding stainless steel and aluminium
Hole pattern#Backing & construction: How the extraction holes in the disc and pad are arranged, for example 6 or 8 holes plus a centre hole. If the holes do not line up, the sander barely extracts any dust; multi-hole discs get round this.See also: Backing padRead more: Which backing pad fits? · Sandpaper for random orbital sanders · Sanding dust: extraction and masks
Hook-and-loop fastening#Backing & construction: Hook-and-loop on the back of the abrasive, with its counterpart on the backing pad. Discs can be changed without tools and reused several times.Read more: Which backing pad fits?

I

Interface pad#Sanders & accessories: A soft foam disc between the backing pad and the sanding disc. It gives a little, follows curves and protects edges – important when sanding paint.Read more: What grit sandpaper for car paint? · Which backing pad for which abrasive?
Intermediate sanding#Work steps: A light sanding between two coats of paint or varnish. It knocks down raised fibres and dust nibs and gives the next coat something to grip.See also: Sanding spongeRead more: Sanding wood before oil or varnish · What grit sandpaper for wood?

M

Matting#Work steps: Lightly scuff sanding glossy paint until the surface is evenly dull – so the next coat has a mechanical key. Usually done with P800 to P1000, foam pads or non-woven abrasive.Read more: Sanding kerb damage on alloy wheels · Keying and painting a radiator
Mesh abrasive#Backing & construction: Grain bonded to an open fabric mesh instead of paper. Dust is extracted through the entire mesh, so the abrasive hardly clogs and lasts longer.See also: Clogging (loading)Read more: Mesh or standard sandpaper? · Sanding stainless steel and aluminium · How to store sandpaper properly
Mill scale#Sanding defects: The hard, dark oxide layer on hot-rolled steel and next to welds. Paint will not stay on it for long; grind it off with P40 to P60 until the metal is evenly bright.Read more: Sanding metal: rust and welds · Which sander for which job?
Multi-hole#Backing & construction: A hole pattern with many small holes instead of a few large ones. The disc fits pads with different hole patterns and extracts dust across its whole surface.Read more: Sanding dust: extraction and masks

O

Orange peel#Sanding defects: A dimpled paint surface that looks like the skin of an orange – usually down to spray pressure, gun distance or thinning. Once cured, it can be levelled wet with P1500 to P3000 and polished out.Read more: Which grit for clear coat?
Orbit (stroke)#Sanders & accessories: The diameter of the circular motion on a random orbital sander, usually 2.5 to 5 mm. A large orbit removes material faster, a small orbit sands finer.Read more: 3 or 5 mm orbit? · What grit sandpaper for car paint? · Which sander for which job?
Orbital sander#Sanders & accessories: A sander with a rectangular pad that oscillates in small circles but does not rotate. It gets into edges and corners well but removes material more slowly than a random orbital sander.See also: Delta sanderRead more: Which sander for which job? · Sandpaper for orbital sanders: size, grit and how it differs from a random orbital sander

P

Paint run (sag)#Sanding defects: Paint that has run down a vertical surface because too much was applied at once. Once fully cured, level it locally with P1500 to P2000 wet and polish.Read more: Which grit for clear coat? · What grit sandpaper for car paint?
Paper weight (A–F)#Backing & construction: The thickness of the paper backing, from A (light and flexible, for fine hand sanding and curves) to F (heavy, for belts and aggressive stock removal). Random orbital discs usually use C- or D-weight paper.Read more: Sandpaper for random orbital sanders
Polishing#Work steps: The step after the finest sanding: polish and a polishing pad remove the last sanding marks until the surface shines again. The finer you sanded beforehand, the less polishing it takes.See also: Dust nib · Orange peel · Paint run (sag)Read more: What grit sandpaper for car paint? · Can you sand out scratches in car paint?
Primer surfacer#Work steps: A sprayable filler primer applied after the body filler: it fills fine scratches and pores and is sanded smooth with P320 to P500 before the top coat.See also: Adhesion promoterRead more: Which grit before painting? · What grit sandpaper for car paint? · What grit for sanding body filler?

R

Random orbital sander#Sanders & accessories: A sander whose pad spins and oscillates in small circles at the same time. The scratch pattern comes out even and directionless – the standard tool for paint, body filler and wooden surfaces.See also: Backing pad · Belt sander · Orbit (stroke) · Orbital sanderRead more: Sandpaper for random orbital sanders · Which backing pad for which abrasive? · How to avoid pigtails and sanding scratches

S

Sand-through#Sanding defects: Accidentally sanding through one layer into the one below – clear coat down to the base coat, paint down to the primer. It happens first on edges and crowns: work there with light pressure and a fine grit, check often, or mask them off beforehand.Read more: Sanding out scratches in car paint · Sanding wood before oil or varnish: which final grit? · Abrasive fleece or sandpaper?
Sanding sponge#Backing & construction: A foam block with grain on one or more sides. It follows profiles and curves, can be rinsed out and suits edges and sanding between coats.Read more: Keying and repainting painted furniture
Scuff sanding (keying)#Work steps: Sanding a sound surface just enough to make it evenly dull so the next coat adheres – without removing it. Usually P400 to P800 on paint, P240 to P320 on wood between coats.See also: MattingRead more: Which grit before painting? · What grit sandpaper for car paint?
Service life#Backing & construction: How long an abrasive keeps cutting before it is blunt or clogged. Dust extraction, light pressure and an open coat all extend it.Read more: When is a sanding disc worn out?
Silicon carbide#Grain & grit: A very hard, sharp abrasive grain that fractures and forms fresh cutting edges as it does. Popular for wet sanding and fine grits on paint, glass and stone.Read more: Wet or dry sanding? · Aluminium oxide, silicon carbide, ceramic: which abrasive grain for what?
Speed#Sanders & accessories: How fast the sander’s pad turns – adjustable on good random orbital sanders. High for stock removal on wood and body filler, lower for plastic, epoxy, clear coat and stainless steel, where too much heat builds up otherwise.Read more: Random orbital sander: 3 or 5 mm orbit? · What grit sandpaper for car paint? · What grit sandpaper for wood?
Stearate coating#Grain & grit: A dry lubricant on the grain that stops the abrasive from clogging with paint or filler dust.Read more: When is a sanding disc worn out?
Swirl marks#Sanding defects: Curly, circular scratches in the finish, often caused by too big a jump between grits, a tilted sander or a loose grain trapped under the disc.Read more: Avoiding pigtails · What grit sandpaper for car paint? · What grit sandpaper for wood?

W

Wet sanding#Work steps: Sanding with water, usually with waterproof sandpaper in the fine grits. The water binds the dust and flushes away debris so the paper does not clog.See also: Silicon carbideRead more: Wet or dry sanding? · Which sander for which job?

Z

Zirconia alumina#Grain & grit: A blended grain of aluminium and zirconium oxide, very tough and self-sharpening under pressure. Typical for heavy stock removal on steel, for example on flap discs and sanding belts.Read more: Sanding metal: rust and welds · Aluminium oxide, silicon carbide, ceramic: which abrasive grain for what?

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