What is Vitrification?
Also referred to as crystallisation or re-crystallisation, this is a method used to achieve a high gloss finish. This procedure is usually used as the final polishing process or for regular maintenance in high traffic areas that require a constant shine such as a hotel reception. It is thought by some people that this is a relatively new method of shining stone however it has in fact been used for around 30 years since its invention in Barcelona.
The method works by creating a chemical reaction on the surface of the stone with the use of steel wool and specially formulated chemical compounds. This is only achievable on stone containing calcium carbonate and so most limestone, marble and travertine can be vitrified where as granite cannot.
How Does It Work?
Most manufacturers of vitrification products will use three main ingredients:
- An acid
- Fluorosilicate compounds
Now it may sound strange to use acid in a product which is used on calcite stone because as we know, acid etches these types of stone. In this case however, the acid is used to break down the bond between the calcium and the carbonate. This allows the fluorosilicate to bond with the calcium to produce calcium fluorosilicate. This process has chemically altered the surface of the stone producing a harder finish.
- Super Shine: The main benefit to this system is that it produces an absolutely amazing shine which can be hard to replicate with polishing powders or diamond grinding alone. It must be remembered however that there is no point in vitrifying a surface which is not clean and scratch-free.
- Durability: Because the surface of the stone has been chemically altered to calcium fluorosilicate, it will have a higher durability and be less porous.
- Slip Resistance: Vitrification can produce a slip-resistant surface
Limitation and Disadvantages
- Orange Peel Effect: Over use of this method can produce a false plastic looking floor. This is very common in many commercial buildings where vitrification is seen as an ‘easy’ way to keep the floor looking shiny. Some vitrification products contain acid which is far too em for its purpose and so over time the floor will develop what is known as ‘orange peeling’. This can best be described as a dimpled plastic look which will certainly be shiny but definitely not the desired result. The floor will almost certainly need re-honing at least in order to remedy the problem.
- Short Lived Results: The super high shine achieved by this process will not last very long if a proper maintenance cycle is not put in place. Certainly in high traffic areas the floor will need to be re-crystallised too often in order to maintain the high gloss appearance.
- Long Term Damage: It is argued by many that crystallizing the stone creates an impervious finish on the surface. Although this may seem like an advantage it is actually detrimental to the life span of the stone. Stone needs to breathe and a surface which is completely impregnable while not allowing moisture to escape will cause the stone to rot over a long period of time. Many people dispute this argument and others still will disregard the implications of this effect because it can take a long time to happen if at all.
Vitrification is a process that is debated so much in our industry with the main question usually asked being ‘Is it better than powder polishing?’
In our opinion, there is no such thing as one system being better than another. Different methods will fulfill different requirements. Vitrifying can be a good short term solution for someone on a low budget as long as they understand the long term effects of the process. On the other hand a client may be adamant that a super high shine is required no matter what the cost to keep regrinding and re-crystallising periodically.
This being said, we will always choose not to vitrify if we have the choice. This is mainly because of the false appearance it can give the stone. We have carried out so many restoration projects where the stone, due to over vitrifying, has taken on a completely different appearance compared to its original texture and colour and the only remedy has been to diamond grind the top layer off. The system is over abused by many unqualified in-house operators who believe that vitrifying alone is a complete maintenance procedure. The inevitable effect is a dirty and discoloured but shiny surface.
We much prefer to use our skill with diamond grinding to achieving a natural shine without the use of harsh acids and fluorosilicates.