1 00:00:00,520 --> 00:00:03,800 Speaker 1: Welcome to Brainstuff from house stuff works dot com where 2 00:00:03,840 --> 00:00:14,720 Speaker 1: smart happens. Hi am rc Brain with today's question, how 3 00:00:14,720 --> 00:00:18,239 Speaker 1: do they get the lead in a wooden pencil? Take 4 00:00:18,280 --> 00:00:20,360 Speaker 1: a look at the writing end of a brand new 5 00:00:20,400 --> 00:00:24,120 Speaker 1: wooden pencil before sharpening it. It appears that the wood 6 00:00:24,160 --> 00:00:27,840 Speaker 1: casing is one solid piece. This might lead you to 7 00:00:27,880 --> 00:00:31,520 Speaker 1: believe that pencil makers bore a hole straight down the 8 00:00:31,520 --> 00:00:34,160 Speaker 1: middle of the wood and then slide in a rod 9 00:00:34,200 --> 00:00:38,760 Speaker 1: of lead. Although early pencils were constructed that way, it's 10 00:00:38,800 --> 00:00:42,760 Speaker 1: not how most wooden pencils are mass produced today. More 11 00:00:42,800 --> 00:00:46,800 Speaker 1: than fourteen billion pencils are produced in the world every year, 12 00:00:47,280 --> 00:00:51,600 Speaker 1: enough to circle the Earth sixty two times. Before discussing 13 00:00:51,600 --> 00:00:54,120 Speaker 1: how the lead is put into the wood casing, let's 14 00:00:54,120 --> 00:00:57,840 Speaker 1: clear up what the lead actually is. Pencil lead is 15 00:00:57,880 --> 00:01:01,240 Speaker 1: not lead at all. It's a combedyation of finely ground 16 00:01:01,280 --> 00:01:04,560 Speaker 1: graphite and clay, mixed with water and pressed together at 17 00:01:04,640 --> 00:01:09,200 Speaker 1: high temperatures into thin rods. We call it lead because 18 00:01:09,240 --> 00:01:12,640 Speaker 1: the Englishman who first discovered graphite believed that they had 19 00:01:12,720 --> 00:01:16,920 Speaker 1: found lad. According to the Cumberland Pencil Museum, in the 20 00:01:16,959 --> 00:01:21,000 Speaker 1: mid sixteenth century, a violent storm knocked over several trees 21 00:01:21,040 --> 00:01:24,720 Speaker 1: in England, uncovering a large deposit of a black substance 22 00:01:25,040 --> 00:01:28,080 Speaker 1: that was first thought to be led. More than two 23 00:01:28,160 --> 00:01:32,400 Speaker 1: hundred years later and English scientists discovered the substance was 24 00:01:32,440 --> 00:01:36,000 Speaker 1: not actually led, but a type of carbon instead. The 25 00:01:36,080 --> 00:01:39,920 Speaker 1: substance was named graphite, after the Greek word meaning to write, 26 00:01:40,319 --> 00:01:44,400 Speaker 1: since that's how people used the substance. Early pencils were 27 00:01:44,520 --> 00:01:48,720 Speaker 1: crude versions of today's standard model. The first pencil was 28 00:01:48,760 --> 00:01:52,480 Speaker 1: a chunk of graphite used by carpenters to make markings 29 00:01:52,560 --> 00:01:56,919 Speaker 1: without denning their materials. This evolved into a graphite chunk 30 00:01:57,000 --> 00:02:01,640 Speaker 1: wrapped in sheepskin, followed by a ring wrap graphite pencil, 31 00:02:02,040 --> 00:02:05,320 Speaker 1: the first pencil with a rod shaped graphite core. To 32 00:02:05,480 --> 00:02:07,920 Speaker 1: use one of these pencils, the writer would have to 33 00:02:08,040 --> 00:02:11,560 Speaker 1: unravel the string as the graphite wore down. The next 34 00:02:11,600 --> 00:02:14,160 Speaker 1: major leap in design was hollowing out a stick of 35 00:02:14,240 --> 00:02:17,320 Speaker 1: cedar and sticking a piece of graphite down the hole, 36 00:02:17,680 --> 00:02:21,920 Speaker 1: an idea often credited to the Italians. The English embraced 37 00:02:21,919 --> 00:02:26,720 Speaker 1: this idea but simplified the manufacturing process considerably. Instead of 38 00:02:26,760 --> 00:02:29,880 Speaker 1: hollowing out a piece of wood, they simply cut a 39 00:02:29,960 --> 00:02:32,880 Speaker 1: groove in the wood. Inserted a piece of graphite and 40 00:02:32,919 --> 00:02:35,160 Speaker 1: broke it off level with the top of the groove. 41 00:02:35,720 --> 00:02:40,760 Speaker 1: Then they glued a small slat on top, encasing the graphite. Today, 42 00:02:40,919 --> 00:02:44,360 Speaker 1: most wooden pencils are mass produced from large blocks of 43 00:02:44,480 --> 00:02:49,200 Speaker 1: cedar cut into slats. A machine cuts eight grooves half 44 00:02:49,240 --> 00:02:52,919 Speaker 1: as deep as the graphite clay rod is thick into 45 00:02:53,040 --> 00:02:56,600 Speaker 1: slats and then places rods in each groove. Once the 46 00:02:56,680 --> 00:02:59,840 Speaker 1: rods are in place, a second groove slat is glued 47 00:02:59,880 --> 00:03:02,640 Speaker 1: on top of the first. When the glue drives, the 48 00:03:02,760 --> 00:03:06,000 Speaker 1: slats are fed through a cutting machine that cuts the 49 00:03:06,040 --> 00:03:09,000 Speaker 1: wood into various shapes and divides the slats into eight 50 00:03:09,040 --> 00:03:13,000 Speaker 1: separate pencils. The seams of the two slats are then 51 00:03:13,280 --> 00:03:16,200 Speaker 1: sanded down and several coats of paint are applied to 52 00:03:16,240 --> 00:03:19,840 Speaker 1: the pencil, giving it the appearance of a single solid structure. 53 00:03:20,720 --> 00:03:23,600 Speaker 1: Do you have any ideas or suggestions for this podcast? 54 00:03:24,000 --> 00:03:26,680 Speaker 1: If so, please send me an email at podcast at 55 00:03:26,680 --> 00:03:29,400 Speaker 1: how stuff works dot com. 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