Gtechniq G4 Nanotech Glass Polish: Real World Test And Review

G4 Nanotech from Gtechniq is a water-based glass polish which uses nano-abrasives and citric acid to deep-clean glass surfaces. G4 is unlike other glass polishes and takes a bit of getting used to, but with practice, it is one of the most effective glass polishes available. It can be used as a stand-alone product, however, a glass cleaner, such as Gtechniq G6 is recommended as a follow-up. 

Prepmycar Rating: 7.5 / 10

Gtechniq Auto G4 Nanotech Glass Polish for Cars, Water Repellent, Removes Dirt and Grime, 100ml

Gtechniq G4 Nanotech Glass Polish

  • 6.0 Application and ease of use
  • 7.0  Residue
  • 9.0 Finish achieved
  • 8.0 Value for money


  • Removes most of the dirt and water spots
  • Very good glass polish
  • Cleansing the surface of contaminates


  • Wax are extremely difficult to remove
  • This product is acidic and has quite a strong smell
  • It should be used in a well-ventilated space, and the wearing of gloves is recommended

Testing process

I tried this glass polish in several scenarios on a few valet jobs cleaning the interior and exterior glass. I also used it extensively around the home, on windows and mirrors. I used a microfibre applicator pad to polish the glass and used a microfibre cloth dampened with G6 to remove any residue. 

Test Results

Application and ease of use 6.0/10

G4 takes a bit of getting used to, and initially, I was frustrated with the poor results I was getting from it, I was surprised as I had never had a bad product from Gtechniq before. My issue was I was using it like many other glass polishes, where you can spread polish across the glass and then wipe away the residue without much issue. 

Very little polish is needed, so little I do not know the exact measurement. What I found worked well was to take the lid of the bottle and place it the applicator on the bottle, then quickly flip it over and back again, which gave enough polish for most windows. This polish is a liquid as opposed to a cream, so pouring it will waste product. 

I used circular motions, which initially crease a haze, which is quite normal. What is important with G4 is to keep working the polish in until it goes clear, meaning the polish has completely diminished. If the polish is not diminished, this residue will cause some problems, more on that later. Sometimes I did need to use a microfibre cloth to remove some residue, adding a spritz of glass cleaner helps in this regard. 

Residue 7.0/10

As mentioned, I initially had some trouble in this area. The first time I used G4 the residue was extremely difficult to remove. I first tried glass cleaner to no avail, then panel wipe, before eventually having to use a clay bar, which lengthened the job significantly. 

Since adjusting my process and ensuring the polish was completely diminished, the residue is less of an issue, except for some spots that needed extra attention. Using very little product and working in small areas are key to controlling residue.

If the residue is left on accidentally, I would recommend using G4 to remove it rather than using a glass cleaner. 

Finish achieved 9.0/10 

I was surprised by just how much dirt was removed from the glass, especially the ones in my house, as shown by the colour of the applicator. It was also able to easily remove water spots, certainly much more effective at that than using a standard glass cleaner and cloth. 

Value for money 8.0/10

A 100 ml bottle of Gtechniq G4 costs around £10.00 ($11.19 USD), which is a higher cost per ml than most other glass polishes. With that said, the very small amount of product needed means this is better value for money than it first seems. Using a quick bottle turn is enough polish to clean an ordinary window, and I estimate this is less than 1 ml of polish, meaning one bottle will be enough for many cars. 

What needs to follow this polish?

G4 is part of the preparation process for applying Gtechniq G1 ceramic glass sealant. After cleaning the car, Gtechniq recommends using G4, followed by G6, before applying the ceramic coating, which will give the best bonding surface. 

Other points to note

This product is acidic and has quite a strong smell. It should be used in a well-ventilated space, and the wearing of gloves is recommended. It is also not to be used on scratch-sensitive surfaces, this includes piano black trim, and rubber trims should also be avoided. 


Gtechniq is a global car care brand founded by physicist Dr Drew Gill in 2001. The company has an extensive range of surface coatings for both automotive and marine applications. The company also produces cleaning products designed to be used in conjunction with their coatings. 

Final thoughts

Initially, I was very frustrated with G4, but now I understand a bit more about it, I find it much more useable. It is a very good glass polish, cleansing the surface of contaminants better than competitors. The amount of buffing required makes it a very tiring product to use, potentially adding to user frustration. 

I do not think it is something I would use unless I was applying a glass coating, with that said, I have used Gtechniq’s glass ceramics before without using G4, with the coating still performing well over a year later. 

Glass polishes are not part of my usually cleaning process, I have never really found a use for them, but as glass polishes go, G4 is an effective one. 


Is G6 glass cleaner still needed when using G4?

It is possible to achieve perfectly clean glass using only G4, however I usually notice some residue left behind. For that reason, it is good to have a glass cleaner like G6 handy.

Is glass polish needed after every wash?

No not at all, I rarely use a glass polish, with glass cleaners being sufficient in most cases.

Will a glass polish remove contaminants from glass?

It will be more effective at removing contamination than a glass cleaner would be, however I find a clay bar is the best way to decontaminate glass.

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Gtechniq Auto G4 Nanotech Glass Polish for Cars, Water Repellent, Removes Dirt and Grime, 100ml
287 Reviews
Gtechniq Auto G4 Nanotech Glass Polish for Cars, Water Repellent, Removes Dirt and Grime, 100ml
  • BETTER VISIBILITY – The high-performance polish cuts through dirt and grime, removing water spots and unwanted tarnishes, providing a clinically clean…
  • CLEANS WITHOUT HARSH CHEMICALS – the unique formulation means you get a smear, scratch-free finish, crystal clear finish every time
  • PREPARES THE SURFACE FOR YOUR CHOSEN GLASS COATING – using G4 is the ideal preparation for G1 ClearVision Smart Glass and G5 Water Repellent Coating…

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