首页
登录
职称英语
Glass is made of mixture of many substances melted together in a large furna
Glass is made of mixture of many substances melted together in a large furna
游客
2024-07-20
10
管理
问题
Glass is made of mixture of many substances melted together in a large furnace. The most important substance is silica which is found in sand. Potash(钾碱), obtained from wood-ashes, is also necessary. To these two substances are added lime, lead, soda and charcoal. Acids are used to remove iron and other impurities. Which might discolor the glass.
The heat of the furnace is so intense that the mixture of these various materials is changed into a boiling liquid. How is liquid glass formed into beautiful or useful objects? Let us imagine that we are watching things being made in a glass factory. It is a small factory in which the work is still done by craftsmen and not by machinery.
Here is a man holding a long iron tube called a blow-pipe. The tube has a wooden mouth-piece to protect the man’s lips from the heat. He puts the other end of the pipe into the molten glass and picks up some of the mixture on the end of the tube. Then he robs the lump of glass to and fro on a metal table, rather like a person rolling pastry. As he rolls it, he shapes the lump roughly into the required form.
Next he lifts the pipe, puts the wooden end to his lips, puffs out his cheeks and blows as you do when you are blowing up a balloon. But of course he has to blow much harder. When the air is blown down into the lump of molten glass a gorge bubble is gradually formed. The craftsman needs both powerful lungs and great skill to ensure that the bubble is of exactly the required size and thickness.
Now you understand why so many hand-made glass objects are round in shape. Handles and feet must be added while the glass is still plastic. When the object is shaped to the craftsman’s satisfaction, it is allowed to cool off. The cooling must be done very gradually. As you know, glass is cracked by extreme and sudden changes of temperature.
Some of the loveliest and many of the most useful things in the world are made of glass. It is most surprising, in view of the great technical skill required, that glass making is a very ancient art. It was practiced thousands of years ago by ancient Egyptians although it was many centuries before men discovered how to make glass transparent.
Glass Making
To remove impurities from the glass,【46】.
Craftsman rolls the molten glass【47】on a metal table.
Glass objects are made【48】.
The mouth-piece of the blow-pipe is【49】.
All glass is【50】.
[br]
选项
答案
transparent
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3685086.html
相关试题推荐
Theteacher,togetherwithherstudents,(go)______tothebeachtoswim.goes句子中主
Wewouldliketohavesamplesofvarioussizesofyourproducttogetherwiththe
I______totheEnglishget-togetherlastnight,butIfellill.A、didcameB、had
Wewouldliketohavesamplesofvarioussizesofyourproducttogetherwiththe
Socialchangeismorelikelytooccurinsocietieswherethereismixtureof
Socialchangeismorelikelytooccurinsocietieswherethereismixtureof
Socialchangeismorelikelytooccurinsocietieswherethereismixtureof
Glassismadeofmixtureofmanysubstancesmeltedtogetherinalargefurna
Glassismadeofmixtureofmanysubstancesmeltedtogetherinalargefurna
Glassismadeofmixtureofmanysubstancesmeltedtogetherinalargefurna
随机试题
LanguageDespitethefactthatmanydefinitionsoflanguagehavebeenproposed,
使用命令“vlanbatch3040”和“vlanbatch30to
Linux中,要查看文件的详细信息,可使用()命令. A.Is-a B
共用题干 护士长让护士小张代表病房参加护士节的护理技术操作大赛,并许诺如果小张
某笔总额10万元,按月付息的贷款,每月支付利息为400元,则该笔贷款的年利率为(
通过打开试验管路阀门检查测试自动喷水灭火系统的湿式报警阀报警功能时,发现压力开关
下列哪一项不是血瘀证的临床表现A.肌肤甲错 B.疼痛如针刺刀割 C.出血血色
根据我国民法典的规定,以下合同中属于实践性合同的是A.买卖合同 B.承揽合同
下列导线中,常用作各种电压等级的长距离输电线路的是()。A.钢芯铝绞线
医疗卫生机构发现不明原因的群体性疾病,应当在2小时内向哪个机构报告A.设区的市级
最新回复
(
0
)