72 | Glass Manufacturing Methods, Molding Methods, Processing Methods Top 10

Hello everyone! 🎵 I took last week off due to a series of business trips, and I'm sorry to say I'll be taking another break for about three weeks starting September 15th as I travel across the US from east to west. Thank you for your understanding.

The glass manufacturing process involves: ① ingredient blending, ② melting, ③ molding, ④ annealing, ⑤ finishing and inspection, and ⑥ packaging and shipping. We've already discussed ① and ②, so now it's time to talk about ③, molding.

Molding is the true essence of glassmaking. Based on techniques that have continued since the Middle Ages, countless senior craftsmen have developed a multitude of techniques and molding methods to create glass.

Although the molding methods for handcrafted glass by artisans and glass produced through automation differ slightly, the fundamental principles are the same. Therefore, I will first discuss the molding methods for handcrafted glass, and then provide supplementary information on automated molding methods.

The main molding methods for handcrafted glass include: ① free-blowing, ② mold-blowing, ③ fine-stem, ④ cane-working, ⑤ pressing, ⑥ squeezing, ⑦ spinning, and ⑧ stretching. In all these methods, glass melted at temperatures above 1300℃ is molded. Molten glass has a consistency similar to corn syrup, so if the temperature is too high, it's too fluid to shape, and if it's too low, it solidifies and cannot be shaped. Glass is molded within a very narrow temperature range. Factors such as seasonal temperature differences, air currents from opening and closing windows, and humidity all influence the process. Maintaining the molten glass material at the optimal state for molding requires delicate control, just as delicate as controlling the melting temperature and conditions.

Free-blowing (chubuki) is a glass forming technique where glass heated to over 1,300°C is gathered onto a cylindrical tool called a "blowpipe." Air is then blown into the blowpipe, expanding the glass to create the product's shape. This technique involves shaping the glass in mid-air without using a mold. Because no mold is used, each piece varies slightly in size, creating a unique, one-of-a-kind work. Additionally, the size changes depending on the artisan's breath strength, so a certain level of skill is required to produce a beautifully shaped piece.

Instead of pouring glass into a mold, the "blown glass" technique, in which molten glass from a melting furnace or similar is attached to a metal tube called a blowpipe (fukizao) and inflated like a balloon by blowing air while rotating the pipe, is said to have been invented around the 1st century BC in Syria. It was named "blown glass" because it is made by gathering glass onto an iron pipe and blowing air through the mouth. The types of glass created include cups, sake cups, bowls, plates, vases, and various other glass vessels.