page_title: Wood finishing
section_title: Removing larger defects
hierarchical_section_title: Wood finishing / Sanding / Removing larger defects
caption_attribution_description: English: Macro photo of a 220 grit sandpaper made of aluminum oxide
context_page_description: Wood finishing refers to the process of refining or protecting a wooden surface, especially in the production of furniture where typically it represents between 5 and 30% of manufacturing costs.
  Finishing is the final step of the manufacturing process that gives wood surfaces desirable characteristics, including enhanced appearance and increased resistance to moisture and other environmental agents. Finishing can also make wood easier to clean and keep it sanitized, sealing pores that can be breeding grounds for bacteria. Finishing can also influence other wood properties, for example tonal qualities of musical instruments and hardness of flooring. In addition, finishing provides a way of giving low-value woods the appearance of ones that are expensive and difficult to obtain.
context_section_description: Larger defects that interfere with wood finishing include dent, gouges, splits and glue spots and smears. These defects should also be removed before finishing, otherwise they will affect the quality of the finished furniture or object. However, it is difficult to completely eliminate large defects from wood surfaces.
  Removing dents from wood surfaces is quite straightforward as pointed out by Flexner. Add a few droplets of demineralized water to the dent and let it soak in. Then put a clean cloth over the dent and place the tip of a hot iron on the cloth that lies immediately above the dent, taking great care not to burn the wood. The transfer of heat from the iron to the wood will cause compressed fibres in the dent to recover their original dimensions. As a result the dent will diminish in size or even disappear completely, although removal of large dents may require a number of wetting and heating cycles. The wood in the recovered dent should then be dried and sanded smooth to match the surrounding wood.
  Gouges and holes in wood are more difficult to repair than dents because wood fibres have been cut, torn and removed from the wood. Larger gouges and splits are best repaired by patching the void with a piece of wood that matches the colour and grain orientation of the wood under repair. Patching wood requires skill, but when done properly it is possible to create a repair that is very difficult to see. An alternative to patching is filling (sometimes known as stopping). Numerous coloured fillers (putties and waxes) are produced commercially and are coloured to match different wood species. Successful filling of voids in wood requires the filler to precisely match the colour and grain pattern of the wood around the void, which is difficult to achieve in practice. Furthermore, filled voids do not behave like wood during subsequent finishing steps, and they age differently to wood. Hence, repairs to wood using fillers may noticeable. Therefore filling is best used with opaque finishes rather than semitransparent finishes, which allow the grain of the wood to be seen.
  Glue smears and droplets are sometimes present around the joints of furniture. They can be removed using a combination of scraping, scrubbing and sanding. These approaches remove surface glue, but not the glue beneath the wood surface. Sub-surface glue will reduce the absorption of stain by wood, and may alter the scratch pattern created by sanding. Both these effects will influence the way in which the wood colours when stains are used to finish the wood. To overcome this problem it may be necessary to locally stain and touch-up areas previously covered by glue to ensure that the finish on such areas matches that of the surrounding wood.
caption: Macro photo of 220 grit sandpaper
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