Glass Forming – The Ultimate Guide

Glass is a widely used material in our day-to-day life. This transparent solid material can be fabricated to serve your various applications in many different ways through a process called glass forming.

What Is Glass Forming

Glass Production Process
Glass Production Process

We can describe glass forming as the process of heating glass at high temperatures and manipulating it in such a way that you create a product. You require a certain temperature range for your glass-forming to take place efficiently.

This is because while forming, your glass will be undergoing cooling and/or reheating as the process continues. Remember that it has to transform from a molten to a semi-solid state before becoming solid and brittle.

Types of Glass Forming Techniques

There are various methods you can apply in the glass-forming process. Each one will depend on the type of glass end product you want and the material requirements of your process.

Let us have a look at some of your options in detail:

· Pressing Method

Glass Pressing Process
Glass Pressing Process

In this glass-forming technique, you have to inject your molten glass into a pre-cast mold of your design. After that, you can put a mold ring on your mold and proceed to press your punch into the mold.

You’re your glass end product is formed between the mold (with its ring) and the punch. This technique can give you products with very accurate shapes with a high production rate.

The downside of this technique is that you cannot form glass products having very thin walls. Additionally, it can produce rough surfaced glass that can contain spots.

· Drawing Method

Glass Drawing Process
Glass Drawing Process

For this technique, you have to have a model that you will use to inject some molten glass inside. You can then mechanically start drawing your glass until your product is formed.

The condition for carrying out this procedure is that you have to do it in a cooler. The formed products you can get from this include glass tubes and flat glass.

· Calendaring Method

Glass Calendaring Process
Glass Calendaring Process

We can also refer to this technique as the rolling method. This is because of the nature of the process where you have to take your molten glass and calendar it on iron rollers.

Alternatively, you can pour your molten glass on a casting table. You can then use a heavy iron roller to flatten it and create your product.

You have to continue calendaring until your glass product is formed to your desired standard. You can use this method to form products such as wired glass and engraved glass.

· Casting Method

Glass Casting
Glass Casting

In this method, you will require a mold designed with your product specifications to create your glass form. Take molten glass and place it inside your mold to fill it.

Cool it down using annealing then process it further using finishing techniques to achieve your final product. You should note that this technique requires very minimal equipment.

However, the accuracy of the casting method is a bit poor in as much as we recommend it for very large products. We mostly use it to create architectural decorations or even art carvings.

· Spinning Method

We recommend this technique for use if you are aiming at creating fine fibers of glass. There is a machine that you can use to spin your molten glass at a very high speed.

These glass fibers have a similar tensile strength as mild steel and they neither shrink nor fade. You can use them for insulating things against heat or sound since they are flexible and soft.

· Blow Method

You will need a blowing pipe to accomplish this technique. You have to scoop the molten glass by dipping the blowpipe and removing a lump of it.

You then gently start blowing glass into the pipe for the molten glass to form a bubble while constantly reheating it. You can continue to blow and heat your glass while shaping it to your desired product form before you cut it off the pipe.

Apart from these other operations include glass cutting and glass annealing.

Glass Manufacturing
Glass Manufacturing

Materials Used In Glass Forming

There are very many materials that you can use as ingredients in glass forming. We can have a general overview of some of the main ones and other additives that are included.

· Silica/Sand

Having a melting point of about 2000°C, silica is what we use as the major component in glass making. You can use silica for the formation of unique and specific products like halogen lamps.

Silica alone is very strong when we compare it with normal glass. However, you have to mix with other ingredients to create additional properties for glass forming.

· Calcium Oxide

We can get this material by extracting it from limestone. Its main aim is to ensure that your forming glass does not dissolve in water.

You can also use either aluminum or magnesium oxides as substitutes for this lime. They can give your glass the enhancement of properties in the same way.

· Sodium Carbonate

The effect of sodium carbonate on your forming glass is that it lowers its melting point to about 1000°C. The result is a more efficient glass-forming process.

However, the resultant mixture may tend to be water soluble and that is where your calcium oxide comes in. The calcium oxide counters this effect therefore your glass retains its non-solubility.

· Additives

If you need to enhance the properties of the glass you want to use in forming, you can include several additives in its manufacture. Some of the additives you can consider include:

  • Lead: if you want to form leaded glasses, then this is the right additive for you. Your final product will have a form of sparkle because of the lead’s reflective nature.
  • Boron: this additive tends to alter how your glass responds to thermal changes. You can use this additive to form Pyrex glass products that are capable of resisting very hot or very cold temperatures.
  • Lanthanum Oxide: this was very commonly used due to its excellent reflective properties. However, due to its radioactivity, we no longer recommend its use as an additive.
  • Color Additives: if you want your glass-forming product to have certain colors, then you can use certain metals and oxides to achieve this. An example is the iron oxide that gives your glass forming a blue-green color mostly used in forming beer bottles.

Applications Of Glass Forming

Glass Accessories
Glass Accessories

You can use glass forming to create anything out of glass. Based on the forming technique you are applying, you can get very many products from glass.

We can have a look at the applications based on the glass forming processes and their products:

  • Blowing produces bottles, balls, etc.
  • The pulling technique produces glass rods or glass tubes
  • You can use pressing to form plates, cups, etc.
  • The calendaring process can give you laminated wire glasses, glass products that have been engraved, etc.
  • We get optical glasses from the casting technique

Conclusion

Glass is a very versatile material that can serve your purpose in many different ways depending on your application. The method you use for glass forming will mainly be dictated by the specific requirements of your application.

You now have a better understanding of the most suitable glass-forming technique that is suitable for your application.

More Resources:

Glass Manufacturing Process – Source: WEPROFAB

What is Glass Batching – Source: WEPROFAB

Glass Tempering Process – Source: WEPROFAB

Producing Glass – Source: WIKIPEDIA

Glass Melting Point – Source: WEPROFAB

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