Why Does The Bottom Of A Glass Bottle Have A Depression？

According to the famous British wine critic Hugh Johnson in his book "The Story of Wine," the grooves in wine bottles were originally used to place hair dryers during bottle making; People also discovered that the groove at the bottom of the bottle has other functions, such as stabilizing the bottle body, so this design became popular.
So let's take a look at how glass bottles from earlier years were made.
Everyone must be familiar with traditional handicrafts such as "blowing glass". Simply put, it's like taking a thin, long, hollow tube, with someone blowing air on one end and a molten glass stick on the other end, adjusting the shape of the gradually expanding glass, similar to blowing bubble gum when I was a child.
And blowing glass bottles can be roughly divided into two steps.
The first step is to blow out a balloon from this molten glass through a tube, which will serve as the bottle body.
The end far from the tube is the bottom of the bottle, and the glass master will take a board to flatten this end; Near the end of the tube is the bottle mouth. The master rotates the tube while using tools to thin and shape the glass embryo.
The second step is to adjust the bottle mouth.
After the previous step, all you need to do is cut off the bottle mouth from the tube, and the bottle is basically formed - but you cannot drink directly from this type of bottle, as the bottle mouth is very sharp and can scratch your mouth!
Therefore, the glass master also needs to take a long stick, dip it in melted glass as glue at one end, stick it to the bottom of the semi-finished bottle, and then extend the bottle mouth into the stove to burn it, making the bottle mouth soft and finely polished and round.
Remember, the glass bottle is still relatively soft at this time. When the glass master hits the bottom of the bottle with a stick, the bottom of the bottle will sink in a little bit.
After removing the stick from the bottom of the glass bottle, traces will inevitably be left at the bottom of the bottle. The bottom of the bottle with traces not only cannot be placed firmly on the table, but also easily leaves scratches on the table - remember that in earlier years, most tables were made of wood.
Therefore, the glass master will use a spray gun to soften and smooth the bottom of the bottle, or directly push the bottom of the bottle inward during shaping.
Overall, the reason why the bottom of a glass wine bottle is sunken may initially be due to a manufacturing issue.
Later on, on the one hand, even with the advancement of technology and the elimination of problems such as unstable placement and scratching the desktop, this traditional design was still preserved; On the other hand, people have found that concave bottle bottoms have other benefits:
As mentioned earlier, some alcoholic beverages containing bubbles can exert pressure on the bottle wall, especially the bottom, when packaged in a bottle. The arched bottom of the bottle has a stronger ability to withstand pressure than the flat bottom and is not easily broken (therefore, the bottom of a cola can is also concave).