Liquid glass / water glass (sodium silicate / Na₂SiO₃) is another choice for making a sand casting mould. The seller told me that after mixing the substances, they will harden the mould by injecting CO₂ to it for industrial use, but in my case he wasn't sure if it would work as my mould is tiny and I haven't got CO₂ and the tools.
I am going to give a try anyway. I didn't inject CO₂ to the first mould either and it worked.
水玻璃（矽酸鈉）是沙／砂模鑄造製模的另一種材料選擇。一般工業使用的沙／砂模，在成型之後會注入二氧化碳，讓模具硬化再進行灌模。
就算我呼一包二氧化碳也沒有工具注進模具體。先試。
矽砂：水玻璃＝10：1，效果尙可，不過沒有經過硬化的砂模的確小鬆軟。壓入模型物的時候比起壓入黏土粉配方模輕鬆，不需要用槌子。可能是因為水玻璃的質地黏滑吧。分離上下模的時候有些矽砂掉落。
I mixed the silica sand and Na₂SiO₃ in the proportion of 10:1 for the first try. The mixture was soft and had a greasy texture, and little silica sand fell from the mould when I separated the top and bottom rings.
I decided to make another mould and leave it for a while, in order to see if a 'hardened' mould would be a better one. I came back after 15 minutes. It looked quite close to the first mould but harder and crispier, and about the same amount of silica sand fell from the mould.
未經過硬化程序的砂模質地比較鬆軟，稍微有外力擠壓就有破碎的可能（還沒製作氣孔與澆鑄通道呢！）。於是我製作第二個砂模，室溫乾燥十五分鐘之後將上下模分開……稍微乾燥之後，砂模硬了一點，不過比較像是心有餘而力不足的硬化～質地變得比較脆些，掉落的矽砂量與第一個砂模相差不多，但比較像是「剝落」而不是「掉落」。
再試。以10：2的比例混合矽砂與水玻璃，第三個砂模的質地，與第二個相差不大，不過質地較黏，分離上下模的時候不夠乾淨俐落（無論是否經過室溫乾燥都是如此），連模型物都黏。
I made the third mould with silica sand and Na₂SiO₃ in a proportion of 10:2. It was not so different to the previous ones, except the texture is stickier so that the mould was not neat and tidy. CO₂ is absolutely needed.
我想我暫時先回到最初的配方吧。
