The making of 30 in telescope - 51, Resilvering

夸克星 註冊時間: 2003-10-09 文章: 2207

Dear ATMers,

Today we successfully finished the silvering of the 30 inch mirror. The freshly prepared silver layer, after polishing by iron III oxide, looks just marvelous.

The reflectivity of fresh silver layer reaches 97% but deteriorate quickly with time. We hope that the telescope could release its power at the first light.

Best regards
Chan Yuk Lun
14-2-2007

主序星 註冊時間: 2006-02-26 文章: 143 來自: 北京

再请教一下陈先生，我采用银镜反应镀镜总发现有乌膜现象[我分析是生成了新的折出物所造成]，上次你镀镜从pp上看，好似用软绵擦乌膜，不知能有更好的方法？但我发现一个现象，在镀吋在镜的垂直面镀的很好，这个问题很是头疼，一直也未找到好的办法。

夸克星 註冊時間: 2003-10-09 文章: 2207

BJDF 寫到:

再请教一下陈先生，我采用银镜反应镀镜总发现有乌膜现象[我分析是生成了新的折出物所造成]，上次你镀镜从pp上看，好似用软绵擦乌膜，不知能有更好的方法？但我发现一个现象，在镀吋在镜的垂直面镀的很好，这个问题很是头疼，一直也未找到好的办法。

Dear Mr. BJDF,

Sorry again I have to write in English. Perhaps Mr. Tong KW may help again !!. ( My big thanks to Mr. Tong )

1. I don't understand your meaning of "black coating". We never encounter such phenomena in silvering process. I guess that the temperature of reaction may affect very much the silvering process. Are you living in Northern part of China where temperature is very low ? In this case the silver may come out too slow and side reaction may take place to contaminate the metallic silver coming out. I am no chemistry expert and this is only my wild guess.

2. In Hong Kong we normally choose a day with temperature around 20 degree Celsius to perform the silvering. The silver just come out very quickly and the whole reaction is finished within two minutes.

3. Due to the enormous size of our mirrors we must perform our reaction with mirror face up. In this way all silver prepcipiated will be caught up by the mirror and there is zero waste. For a 30 inch mirror huge amount of silver nitrate has to be used and silver nitrate is very expensive stuff. We need to save money as much as possible.

4. During the end of reaction brown muddy substance ( I don't know what they are ) will form and drop onto the silver surface. We rinse the surface by tap water and then, with the whole siver surface subnmerged into tap water, we wash out the muddy coating ( is it what you mean the "black coat" ?) very gently by cotton pad. This process has to be carried out inside water otherwise the silver wil be scratched away.

5. Above process cannot gaurantee complete removal of the "muddy coating". The final step is to let the mirror rest in vertical position and wait until complete dry off. Once the silver turns dry it becomes hard enough. We then dry polish the surface by iron oxide, using deer skin as polishing pad. Adfter this final stage the silver will appear to be very bright and shinny, as you could see in the above attached picture.

My suggestion is that if you could choose you should send your mirror for aluminium coating rather than attempting silvering by yourself. The life of silver is short and there is no protection overcoat available on silver. Unlike you we don't have a choice, for our mirrors are being too big.

Best regards
Chan Yuk Lun

主序星 註冊時間: 2006-02-26 文章: 143 來自: 北京

还请TONGKW先生邦翻一下吧，谢ろ Razz

白矮星 註冊時間: 2006-05-19 文章: 639

讓我也試譯一下吧，有些地方自己都不太熟，譯得不準確請各位指正。

1.我不明白你所指的'烏膜'是什麼。我們鍍銀時從未遇過這種現象。我估計反應的溫度對鍍銀的過程有很大的影響。你住在華北、氣溫很低的地區嗎？如果這樣，產生金屬銀的化學反應可能較慢，結果其他化學反應的副產品會污染銀膜。我不是化學專家，這只是我胡亂猜測。

2.在香港，我們通常會選擇溫度大概攝氏20度的日子進行鍍銀。產生金屬銀的過程非常快，整個過程不過兩分鐘。

3.因為我們的鏡太大，所以我們必須鏡面向上來進行鍍銀。因此，所有的銀都會沉澱在鏡面，不會浪費。鍍一塊30寸的鏡需要很大量的硝酸銀，而硝酸銀是十分昂貴的。我們必須盡量節省金錢。

4.在化學反應的尾聲，一些棕色、泥土狀的物質會出現(不知是什麼)，並落在銀膜上。我們會用自來水沖洗鏡的表面，然後將整塊鏡面浸在自來水中
，用棉花球輕輕地洗去那些泥土狀的物質(難道這些就是你所說的"烏膜"？)這個過程必須在水中進行，否則會劃花銀膜。

5. 以上過程不能保證"泥狀外層"能被完全清除。最後一個步驟是將鏡垂直放好，等待鏡面乾透。乾透後銀膜會變得足夠硬。然後我們會用氧化鐵進行乾拋光，用鹿皮做拋光布。經過這最後一步，鏡面會變得十分光亮，正如以上的貼圖。

如果可以的話，我建議你把鏡送去專業鍍鋁，因為鍍銀的壽命很短，現時又沒有適合銀面的保護膜。我們的鏡太大，實在沒辦法才自己鍍銀而已。

主序星 註冊時間: 2006-02-26 文章: 143 來自: 北京

先谢xiaoer先生的翻译。
回陈先生；正是这种泥状物，但與银膜结合的很紧，不用力擦不掉，一用力就伤银膜。

夸克星 註冊時間: 2003-10-09 文章: 2207

BJDF 寫到:

先谢xiaoer先生的翻译。
回陈先生；正是这种泥状物，但與银膜结合的很紧，不用力擦不掉，一用力就伤银膜。

Dear Mr. BDJF,

If the mirror is not very big ( below 10 inch aperture )this muddy coating may be whipped out inside water before the drying process of silver surface.

However for really big mirror it is impossible to completely whip the silver surface clean inside water. Iron III oxide dry polishing is a must. If you use old Camois skin for dry polishing the danger of scraching the silver surface is minimized, although some sleeks are unavoiably left behind.

Best regards
Chan Yuk Lun

中子星 註冊時間: 2005-09-13 文章: 1495 來自: Hong Kong

陳先生回覆BJDF
如果那只反射鏡不是很大（ 10 英吋口徑以下）則此泥狀被覆物可以在銀膜表面的乾燥程序進行之前在水中被抹走。
無論如何，實在很大的反射鏡就不可能在水中將鍍了銀的表面完全抹淨，這就一定需要用氧化鐵進行乾拋光。你如果採用舊的輭皮（用羊皮或鹿皮等製成之）來進行乾拋光就會將抓傷鍍了銀表面的危險減至最小程度，雖然無可避免會留下一些光滑面。

主序星 註冊時間: 2006-02-26 文章: 143 來自: 北京

谢翻译。