Grade 10 woodwork – Surface preparation Quiz
1. What is the first thing you should do before starting surface preparation on a wooden classroom bench?
Inspection identifies defects that need repair or removal before sanding or finishing, ensuring a good final result and safe use.
2. When sanding a wooden school desk by hand, which direction gives the smoothest finish?
Sanding along the grain avoids scratching across fibres and prevents visible marks, giving a smoother final surface.
3. Which tool is best for removing old varnish or paint from a small timber sample before refinishing?
A hand scraper removes old finish without deep gouging and allows controlled removal on small areas before sanding and re-finishing.
4. Why should you progress from coarse to fine sandpaper grades when preparing a timber surface?
Coarse grades remove high spots and defects; finer grades smooth scratches left by coarser paper, producing a uniform surface for finishing.
5. What problem can occur if you sand across the grain on softwoods like pine?
Sanding across the grain on softwoods can lift and tear fibres, causing rough patches that spoil appearance and require extra work to fix.
6. Which is the correct way to prepare the end grain before applying stain?
End grain soaks up finish more than face grain; sealing it first prevents blotchy, uneven staining and improves final appearance.
7. What is the purpose of using a tack cloth or clean rag after sanding?
Dust left on the surface interferes with adhesion and causes imperfect finishes; a tack cloth or damp rag removes dust before finishing.
8. Which safety equipment is most important when sanding timber in a school workshop?
Sanding produces fine dust that can harm the lungs; a dust mask or respirator protects respiratory health during surface preparation.
9. What does 'raising the grain' mean and how is it corrected during preparation?
Wetting raises fibres making the surface rough; once dry, a light sanding smooths the raised grain before finishing.
10. Which filler is most suitable for filling small dents and screw holes in interior furniture before finishing?
Water-based wood filler is designed for timber: it fills defects, sands smoothly and accepts stain or finish for a uniform look.
11. Why should you sand between coats of varnish or paint?
Light sanding between coats smooths imperfections and creates a slightly rough surface that helps the next coat bond and gives a better finish.
12. What grit of sandpaper is appropriate for initial sanding of rough-sawn timber?
Rough-sawn timber needs coarse paper (60-80) to remove major high spots and quickly shape the surface before finer sanding.
13. How should electric sanders be used to avoid creating dips or gouges in the wood?
Leaving an electric sander in one place or pressing hard removes too much material and makes uneven dips; steady movement prevents gouging.
14. What is 'feathering' a repair in surface preparation?
Feathering smooths the transition between filled and original surface so repairs are not visible after finishing.
15. Before applying oil finish to a desk made of hardwood, which preparation step improves finish absorption?
Fine sanding cleans and slightly opens pores improving oil penetration and producing a more even and durable finish.
16. Which method is best for removing grease or wax contamination from a wood surface before finishing?
Grease and wax repel finishes; a suitable solvent removes contaminants so finishes can adhere properly.
17. What is the purpose of chamfering or rounding sharp edges before finishing school furniture?
Rounding edges prevents sharp corners that cause splinters, wear easily, and helps coatings resist chipping for longer life.
18. Which sign indicates that a timber surface still has finish dust before applying a new coat?
Powdery smearable dust shows sanding dust or old finish particles remain; these must be removed for good adhesion of the next coat.
19. When preparing plywood for painting in a Kenyan school workshop, why should you pay attention to edges and joints?
Edges and joints are more porous and can soak up paint causing visible differences; sealing or filling ensures a uniform appearance.
20. What is the correct action if you notice a raised knot on a school desk during surface preparation?
Raised knots can cause uneven finish and can come loose; sanding and using a knot sealer or filler stabilises them for a reliable finish.
21. Which of the following best describes a 'binder' in a wood finish product used after surface preparation?
Binders (resins) are the film-forming part of finishes like varnish or paint that hold pigments and adhere to the wood surface.
22. Why should you avoid using very oily rags for cleaning timber surfaces before finishing?
Oils repel finish products and can lead to poor adhesion, blotching or defects; surfaces must be free from oils before finishing.
23. What is the effect of not allowing filler or glue to dry fully before sanding during surface preparation?
Sanding uncured filler or glue gums the paper and leaves an uneven surface; full drying ensures clean sanding and good finish.
24. Which finish is most likely to highlight flaws if surface preparation is poor?
High-gloss finishes reflect light and make scratches, bumps and dust more visible, so they require very careful preparation.
25. What is the correct disposal method for used solvent-soaked rags in a school workshop to prevent fire risk?
Solvent-soaked rags can spontaneously combust; storing them safely in a sealed metal container reduces fire risk and allows proper disposal.
26. What is the main purpose of surface preparation before applying a finish to a wooden product?
Surface preparation removes roughness, glue, dirt and other defects so stains or paints adhere evenly and the final appearance is smooth and durable.
27. When sanding a plank by hand, which sanding motion gives the smoothest result and reduces scratch marks?
Sanding with the grain avoids noticeable cross-grain scratches and produces an even surface suitable for finishing.
28. Which sequence of sandpaper grit is best for preparing a hardwood surface before finishing?
Progressively finer grits remove earlier scratches and smooth the wood step by step; starting too fine leaves existing rough cuts.
29. Why should raised grain be removed or controlled before applying water-based finishes?
Water raises the wood fibres; if they are not smoothed (often by dampening and re-sanding), the finish will look rough as fibres stand up.
30. What should you do to prepare end grain before finishing to avoid dark or blotchy stains?
End grain soaks up finish quickly and unevenly; sealing it first ensures more consistent absorption and uniform colour.
31. Which is the correct use of wood filler when preparing a surface for finishing?
Filler is used to repair defects like holes and cracks so the surface becomes even and ready for a uniform finish.
32. Which tool is best for producing a flat, smooth surface quickly on a rough board before sanding?
A hand plane removes thin layers of wood across the face to produce a flat, smooth surface faster than sanding alone.
33. Why is it important to remove sanding dust before applying paint or varnish?
Dust particles trapped under the finish produce roughness and weak adhesion; cleaning ensures a smooth, durable coat.
34. Which cleaning method is best after final sanding and before finishing?
A tack cloth or slightly damp lint-free cloth removes fine dust without leaving residues, preparing the surface for even finishing.
35. When preparing wood for staining, why is it important to sand evenly and in the right direction?
Stain highlights surface differences; uneven sanding produces uneven absorption and visible blotches.
36. What is the purpose of a sanding sealer used before finishing?
Sanding sealer partially fills pores, allowing easier final sanding and creating a consistent surface for topcoats to adhere to.
37. Which grit of sandpaper is most appropriate for smoothing a previously planed surface before final sanding?
80–120 grit removes minor tool marks from planing without digging deep scratches and is a suitable starting point before finer sanding.
38. Why should sanding be done progressively from coarse to fine rather than starting fine?
Progressing from coarse to fine ensures defects are removed and earlier scratches are eliminated, producing a smooth final surface.
39. What safety step should you always take when sanding and preparing wood surfaces?
Sanding produces fine dust that can harm lungs and eyes; a dust mask and eye protection keep you safe.
40. If a wooden surface shows tear-out while planing, what is the best corrective action during surface preparation?
Tear-out is caused by dull blades or aggressive cuts; sharpening the blade and cutting with the grain or taking shallower cuts prevents tear-out.
41. Which product is best to remove grease or oil stains from a wooden workpiece before finishing?
Grease and oil must be dissolved or lifted with an appropriate solvent; mineral spirits remove oily contaminants without damaging wood when used correctly.
42. When preparing a previously painted surface for repainting, which step is essential?
New paint must adhere to a sound, keyed surface; removing loose paint and light sanding ensures good bonding of the new coat.
43. Which is the correct order when preparing for varnishing a tabletop?
A flattened, dust-free surface with appropriate sealing provides the best base for varnish to form a smooth, durable finish.
44. Why is it recommended to sand joints and glued areas lightly after glue has cured?
Excess dried glue should be removed and the joint smoothed so it blends with the surface before finishing.
45. Which type of abrasive is best for final smoothing before applying a stain on softwood like pine?
Fine sandpaper leaves a smooth surface suitable for even staining on softwoods, removing minor defects without deep scratches.
46. What problem occurs if you sand stained wood too much before applying a finish?
Excessive sanding can remove or thin the stain, causing uneven colour and spotty areas under the final finish.
47. Which practice helps avoid visible lap lines when applying stain or finish to a flat panel?
Working wet edge to wet edge prevents overlap marks by keeping a continuous workable area where the finish can level and blend.
48. When should you use a scraper instead of sandpaper during surface preparation?
A cabinet scraper can remove finish and small defects smoothly, especially on figured wood where sandpaper may clog or cause tear-out.
49. What is the main reason to let wood acclimatize in the workshop before surface preparation and finishing?
Wood that is not acclimatised may move after finishing, causing cracks or finish failure; stabilising moisture content first prevents this.
50. Why should you avoid touching a freshly sanded surface with bare hands before finishing?
Oils and salts from skin can cause blotchy finishes or adhesion problems; handle with clean gloves or avoid touching the sanded areas.
51. What is the correct action if you find small cracks (checking) on a surface during preparation?
Small cracks should be filled with a compatible filler, allowed to cure, and sanded so the finish will be even and the defect won't show.