Penetrating Sealers: Are they really invisible?

One question that comes up every time penetrating sealers are discussed is do they change the colour of the stone or tile? With today’s technology the answer is invariably no – they are invisible. However when you apply almost all of the penetrating sealers on the market they will subtly change the colour of some surfaces. This is the reason we at Aqua Mix state that our penetrating sealers have a “natural” look. However in most cases any subtle change in colour will not last. Understanding how penetrating sealers can alter the colour or tone of a sealed surface is imperative to making customers comfortable with this sealer characteristic.

When any penetrating sealer is applied two things happen. Firstly the majority of the sealer is absorbed below the surface and secondly a small amount of sealer residue is left on the surface. It is a combination of these two elements that can create a colour or tonal change to the surface. When light hits any surface the colour we see depends on the amount and frequency of the spectrum that is reflected back to our eye. In many cases parts of the spectrum are actually absorbed into a surface, scattered and then reflected back in a totally altered state. The sealer that is absorbed into the surface as well as the residue left on top can further alter the reflected light creating a colour or tonal variation when compared to the same surface unsealed.  This is the same reason why stone looks darker when it is wet. A wet stone is actually closer to the real colour of the stone than dry because the dry stone reflects much closer to white light. This phenomenon is actually happening on all stone and tile when sealed with any sealer. However whether we actually see or perceive a change in colour depends on the surface characteristics (texture and colour) as well as the type of sealer applied.

The type of polymers or active ingredients used in sealers as well as the carriers influence how the sealer will react with the spectrum and hence the colour we see. However with contemporary sealer technology it is the carrier that transports the actual sealer ingredients that plays by far the greatest role. The two main carriers used today are water and solvent (using the word solvent to include alcohol).Of the two it is solvents that create the largest amount of colour change. This is because firstly water tends to evaporate leaving any residue on the surface as only the active sealer ingredients and most of these are absorbed below the surface anyway. In contrast many of the solvent carriers do not totally evaporate leaving a surface residue made up of carrier and a small amount of sealer ingredient. It is this residue that alters the spectrum by generally absorbing light and in doing so reflecting back a colour that is darker and like a wet surface closer to the actual colour of the stone or tile.  This explains the reason why Aqua Mix Ultra Solv can subtly enhance the colour of some surfaces more than our water based Sealers Choice.

However it must be noted that the change in colour created on some sealed surfaces by contemporary penetrating type sealers is usually so minimal that if you put some space between a sealed and unsealed piece the tonal change can no longer be seen. The change in colour is also usually much less than the natural colour variation between pieces of the same surface and is much less than the change in colour created by natural soiling once the surface is in service. It is also important to note that in most cases any colour enhancement will not last due to the fact that penetrating sealers are not formulated to withstand abrasion and hence the light altering surface residue will very quickly be worn away. For those that require true long lasting colour enhancement from a penetrating sealer Aqua Mix manufacture Enrich N Seal that utilizes spectrum alteration. However this is achieved by the cured absorbed polymer rather than by leaving a temporary surface residue.

In conclusion all contemporary water and solvent based penetrating sealers can in some instances subtly change the colour of natural stone. However in most cases the eye simply cannot see this change hence the tag of being invisible. Whether you can see a change or not is due to the interaction of the sealer, the stone, and the wave length and part of the spectrum that is reflected back to your eye. However most importantly in most cases this does not affect the actual performance of the sealer or its practical working life. 

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