Quality Control of Glass Bottles


Glass is a very valuable material because of its heat resistance, versatility, and transparency, adaptability. Furthermore, it is very recyclable and cheap to produce. A glass container does not react with the contents it is filled with since it is chemically inert. Glass is one of the most popular and versatile building materials due to all these factors and more.

When inspecting glasses and maintaining quality, several tests are used during the pre-production and production-manufacturing stages. In this article, we explore the composition of glass and the various quality control tests for glass bottles.

Composition of Glass

Glass could be viewed as a form of liquid sand. The composition of different types of glass will vary slightly. Still, in general, glass is made of sand, sodium carbonate, calcium carbonate, other recycled glass, and a lot of heat.

Sand melts at a very high temperature of 3090 ° F. Sand completely transforms as it reaches its melting point. As it becomes amorphous— not quite a solid and not quite a liquid—the structure changes. This unique chemical produces a moldable material used to make glass.

Manufacture of Glass

To make glass, sand is mixed with sodium carbonate and calcium carbonate, before it is recycled glass in a commercial glass plant. Then, a furnace is used to heat these materials. Once it has reached a liquid state, it is poured into molds to take on desired shapes or onto a flat surface to form glass sheets.

Exact ingredients and processes of glass making differ based on the type of glass made. For instance, additional chemicals are used to produce colored glass. To create oven-proof glass, boron oxide is added.

Quality Control Tests for Glass Bottles

Glass Bottles Chemical Resistance

The resistance of glass bottles to some chemicals is ascertained through the following tests:

  • Powdered Glass Test

This test is performed to estimate the amount of alkaline typically leached from a powdered glass at high temperatures. The alkaline leaching increases when the glass is powdered, and it can be measured with 0.02N sulfuric acid applying methyl red as an indicator.

Procedure: in a 250 ml flask, a 10 g sample and 50 ml of high-purity water are added. Put it in an oven for 30 minutes at 121⁰C±2⁰C. Cool it under running water and place the solution in a new flask. Wash it with 15ml of deionized water and then decant it again. Using methyl red as an indicator, titrate instantly with 0.02N sulfuric acid, and note the volume.

  • Water Attack Test

This only applies to treated soda lime glass bottles with controlled humidity levels, which neutralize the surface alkaline and increase the chemical resistance of the glass. The key factor is whether or not the alkali leached from the bottle’s surface.

The procedure is followed adroitly. High-purity water is used to rinse the bottle completely. Each bottle is filled with water to 90% of its overflow capacity, autoclaved at 1210°C for 30 minutes, and cooled. The liquid is decanted into another bottle before titration with 0.02N sulfuric acid with methyl red as an indicator. The amount of alkali oxides found in the glass bottles is determined by the volume of sulfuric acid used.

Glass Bottles Hydrolytic Resistance

Rinse each bottle at least three times in CO2-free water before filling it to the appropriate level. Also, fill and cover the bottles and vials, then store them in the oven.

Let the steam come out of the vent cork after heating to 100⁰C for 10min. In 20 minutes, raise the temperature from 100⁰C to 121⁰C. The temperature is between 121⁰C and 122⁰C for 60 minutes. To avoid a vacuum, lower the temperature from 121⁰C to 100⁰C over 40 minutes of venting. After cooling and combining the liquids under examination, remove the bottle from the oven.

  • Arsenic Test

Glass bottles meant for aqueous parenteral are the subject of this test. Wash the bottle’s interior and exterior with clean, distilled water for five minutes. Prepare the test according to the instructions in the test for hydrolytic resistance for a sufficient number of samples to yield 50ml. From the combined contents of all ampoules, pipette 10 ml of the solution into the flask.

Add 10ml of HNO3 to the water bath to dry it, dry the residues at 1300C for 30 minutes, let them cool, and then add 10ml of hydrogen molybdate reagent. Heat in a water bath while stirring to dissolve for 25 minutes. Calculate the absorbance at 840 nm after cooling to room temperature. Use 10 ml of hydrogen molybdate for the blank.

  • Thermal Shock Test

Place the samples in a tray standing upright. Place the tray in hot water for a predetermined amount of time before transferring it to a cold water bath. Before and after the test, look for any cracks or breaks.

A bottle’s size, design, and glass distribution affect how much thermal shock it can sustain. The temperature range for small bottles is 60 to 80⁰C, and for a pint bottle, it is 30 to 40⁰C. The temperature difference between hot and cold water in a typical test is 45⁰C.

Pressure Test of Internal Bursting

The Glass Research Increment Pressure Tester of America is the most often used tool. The test bottle is put into the test chamber after being filled with water. Applying a scaling head causes the internal pressure to rise automatically in a succession of steps, each of which is maintained for a certain amount of time. A preset pressure level can be verified on the bottle, and the test can go on until the bottle ultimately explodes.

  • Leakage Test

A drug-filled bottle is put inside a container that contains a colored solution (dyed solution) that is under higher pressure than the pressure inside the glass bottle. It ensures that colored solution will seep into the container if leaks or breaks occur.

  • Test for Vertical Load

A vertical force is imparted to the bottle by carefully placing it between a fixed platform and a hydraulic ramp platform raised gradually. The vertical load is registered on a pressure gauge.


Glass is one of the important materials when it comes to building and other industries today. This makes it important to employ the best means to ascertain and control quality in glass manufacture. The processes of glass inspection and testing involve a lot of technicalities. To avoid errors, consider engaging the services of EC Global Inspection. We are the best option for you.