Just until a few decades earlier, people perhaps found it very difficult for engraving on glass and metals. They had only a few techniques such as sandblasting for creating etchings on glass.
Simultaneously a constant effort was always there to develop a craft for making exceptional products. You can buy glass products via https://crystalsensations.com/decorative-methods/sub-surface-laser-engraving/.
Glass workers suffered from loss and were sometimes penalized for not having the right tools or means. On the other hand, a significant amount of time had also to be invested to get the process done.
Then the technique of glass engraving was discovered. This is an effective and less time-consuming process. Thanks to these modern techniques that clients now have the advantage of buying stylish glass blocks where pictures of loved ones or lines of choice may be engraved without having to spend too much time or money.
The sophisticated machinery used nowadays by people is capable of engraving in several objects besides glass. Be it metal or wood, this has become a very simple affair.
Going one step ahead, there has been less use of manual labor in such processes. This has been made possible through the use of computers and software. Now, there are lesser chances of mistakes and blunders as such.
All one needs to do is to enter the right information correctly and the computer will generate 3D images and texts as previews, after which the final command may be given.
You can look for techniques to clean these in books or on the internet and you will see that there are techniques of using a detergent, ammonia, or a chemical for cleaning off dust or even the worst stain on these products.