{"id":22896,"date":"2019-04-18T12:28:06","date_gmt":"2019-04-18T09:28:06","guid":{"rendered":"https:\/\/revistadinlemn.ro\/?p=22896"},"modified":"2024-03-03T22:59:22","modified_gmt":"2024-03-03T20:59:22","slug":"overzealous-mistakes-when-sanding-wood-by-hand","status":"publish","type":"post","link":"https:\/\/revistadinlemn.ro\/en\/2019\/04\/18\/greseli-din-exces-de-zel-la-slefuirea-manuala-a-lemnului\/","title":{"rendered":"Overzealous mistakes when sanding wood by hand"},"content":{"rendered":"

I had a conversation with someone who, after having converted a kitchen furniture, had a problem with the paint cracking on the wood and didn't know what had happened. Convinced that the paint was good, he thought he might have done something wrong. He described the technology to me point by point and that's when I understood how you can end up with a poor result by doing more than necessary in your desire to be as close to perfection as possible. In short, transformation involves 3 steps: cleaning down to the wood<\/a>, hand sanding<\/a> and repainting. The sanding of the wood had been done very carefully, in increments from 100 grit to 500. The paint was then applied in thin coats, waiting for the required drying time, and yet, after drying, the paint began to crack. What happened? Where is the mistake?<\/p>\n

Sanding wood by hand<\/span><\/h5>\n

It is necessary to sand the wood before applying the stain and varnish (paint) in order to obtain a uniform color, to ensure that the film has good adhesion and that the wood has a pleasant grain, does not scratch to the touch.<\/p>\n

Good adhesion means good varnish\/paint absorption into the wood. Wood absorbs naturally through the fiber channels (visible in some species as pores), exactly where the water circulated when it was a tree. Where it absorbs best is where the fibers are sectioned. This is where the so-called fiber ends appear, where the liquid enters easily.<\/p>\n

Sanding has this ability to open fiber ends. But, paradoxically, it can also close them, limiting absorption into the wood. How do we know whether we are opening or closing the fiber? By choosing the right abrasive paper or sponges to sand with.<\/p>\n

Wood sanding paper grain<\/span><\/h5>\n

I won't go into the sandpaper in detail. I have done it on another occasion and you can find details\u00a0here<\/a>. I just want to point out that the numbers written on this paper have a meaning and are very important. By choosing the paper according to them you will get a quality sanding. The grit is represented by numbers from 40, 60, 80 to 400, 500, 600. The higher the number, the finer the paper and the less it scratches. The very abrasive paper with small numbers is used for wood, and the finer paper is used for sanding between coats of primer, varnish or paint.<\/p>\n

The fiber ends open if sanding paper is used up to 180, maximum 220, and this is for the more loose and soft-grained, soft-grained wood species such as poplar<\/a>. In hard species such as oak tree<\/a>, we can stop at 150 no problem. Abrasive papers finer than that no longer have the power to break the fiber open. On the contrary, they will push the already open fibers into the wood, closing the absorption channels. The fine dust resulting from sanding with fine paper also contributes to the closing of the channels, which will only \"grind\" the wood fiber without opening it.<\/p>\n

This is what happened in the case described. When the wood reached 500 grain, it was totally \"closed\", it could not absorb any of the paint applied. The film formed was in fact a paint droplet on top of the wood, trapped only from place to place. With no adhesion to the substrate, this very thin suspended layer immediately \"cracks\" at the slightest movement or touch.<\/p>\n

Why progressive sanding<\/span><\/h5>\n

From the above, the question arises: so why is it necessary to sand progressively finer and finer? Weren't the fibers opened by 40 or 60? Why not stop there? Because the wood would absorb a lot and uncontrollably. In the case of stain, stains would automatically appear, and in the case of paint or varnish, the large amount absorbed deep into the wood means losses. Therefore, it is recommended that the first coat of the finish (after staining, if necessary) should be grund<\/a> or the lacquer\/paint should be more diluted. This will allow it to penetrate into the surface of the wood, grip the grain well and the resulting film to adhere.<\/p>\n

By sanding the wood progressively, the first few grits break up the grain, and the next few close the grain a little so that absorption is more controlled. This also limits and reduces the size of the broken fibers, which will be loaded with varnish and will rise, giving a rough appearance after varnishing. If we stopped at 40 grit, these fiber ends would be very large. Loading them with varnish would result in real wood spikes that would be very difficult to smooth through sanding between layers<\/a>. You would need to insist, maybe even use thicker paper, below the recommended thickness (240 and up), which will almost remove that first coat of varnish. Obviously, that means waste and \"labor in vain\".<\/p>\n

In conclusion ...<\/span><\/h5>\n

Do not try to make the wood as smooth as possible because you will reduce the adhesion of the varnishes or paints used. Do not leave the sanded wood with only very small grain sizes (40, 60) because you will get a stained and dark wood or you will unnecessarily consume primer\/lacquer\/paint and sandpaper trying to get the smoothest and most pleasant to the touch surfaces.<\/p>\n

I hope I have managed to explain what happened in this situation in a way that everyone can understand. If there are any questions or comments below. And if you know someone who would benefit from this information, share the article with them.<\/p>","protected":false},"excerpt":{"rendered":"

Am avut o discu\u021bie cu cineva care, dup\u0103 ce a transformat un mobilier de buc\u0103t\u0103rie, avea o problem\u0103 cu cr\u0103parea vopselei aplicate pe lemn \u0219i nu \u0219tia ce s-a \u00eent\u00e2mplat. Convins fiind c\u0103 vopseaua era bun\u0103, se g\u00e2ndea c\u0103 este posibil s\u0103 fi f\u0103cut el ceva gre\u0219it. Mi-a descris tehnologia punct cu punct \u0219i atunci […]<\/p>\n","protected":false},"author":5,"featured_media":22993,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"2176","_seopress_titles_title":"","_seopress_titles_desc":"\u0218lefuirea manual\u0103 a lemnului deschide capetele de fibr\u0103. Dar, poate s\u0103 le \u0219i \u00eenchid\u0103, limit\u00e2nd absorb\u021bia \u00een lemn. Cum \u0219tim c\u0103 deschidem sau \u00eenchidem fibra?","_seopress_robots_index":"","footnotes":""},"categories":[2185,2176],"tags":[350],"class_list":["post-22896","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-finisare-diy","category-slefuire","tag-slefuire"],"_links":{"self":[{"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/posts\/22896","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/comments?post=22896"}],"version-history":[{"count":18,"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/posts\/22896\/revisions"}],"predecessor-version":[{"id":37866,"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/posts\/22896\/revisions\/37866"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/media\/22993"}],"wp:attachment":[{"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/media?parent=22896"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/categories?post=22896"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistadinlemn.ro\/en\/wp-json\/wp\/v2\/tags?post=22896"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}