18th March 2021

Glassflake Ltd manufacture glass flakes made from a special borosilicate glass and other types of glass. This glass, manufactured with thickness grades between 350 nm and 1μm is used extensively in the cosmetics industry.

A couple of years ago we carried out research into adding different grades of our calcium borosilicate Glassflakes and other glass formulations into sun screens. We found that on its own the glass flakes did very little but when added to some existing sunscreens it became a very significant booster. It was found that we could boost an existing SPF15 sunscreen to as high as SPF85 with the addition of only 1% by weight. However, due to other research work priorities this was not pursued further.

Recently we came across this article  in the Cosmetics & Toiletries magazine and our interest was renewed.

The chart below shows how the product Glassflake Gold at thickness of 1um or 500nm affects the SPF of various sunscreens designated as SPF15 by the manufacturer:


Sample SPF (mean)
Garnier SPF15 14
Garnier SPF15+0.1% gold 500nm, d(0.5)8µm 87
Garnier SPF15+1% gold 500nm, d(0.5)8µm 97
Garnier SPF15+0.1% gold 1 µm, d(0.5)8µm 42
Garnier SPF15+1% gold 1 µm, d(0.5)8µm 52
Nivea SPF15 24
Nivea SPF15+0.1% gold 500nm, d(0.5)8µm 15
Nivea SPF15+1% gold 500nm, d(0.5)8µm 17
Nivea SPF15+0.1% gold 1 µm, d(0.5)8µm 17
Nivea SPF15+1% gold 1 µm, d(0.5)8µm 38
Nivea SPF15+1% gold2.37µm, d(0.5)8µm 16
Nivea SPF15+1% gold 500nm, d(0.5)20µm 43
Nivea SPF15+3% gold 500nm, d(0.5)8µm 31
Soltan SPF15 11
Soltan SPF15+0.1% gold 500nm, d(0.5)8µm 14
Soltan SPF15+1% gold 500nm, d(0.5)8µm 93
Soltan SPF15+0.1% gold 1µm, d(0.5)8µm 41
Soltan SPF15+1% gold 1µm, d(0.5)8µm 50

It is interesting to note the differences in effect between the various sunscreens and how the thickness of flake and addition level affects.

It is also interesting to look at the change in wave length absorbance between the different sunscreens:



We also looked at the reflectance using different Glassflakes designated AZ40, AZ41 and AZ42. These are calcium borosilicate flakes coated by wet chemistry with TiO2. The AZ40 which had a thick layer of TiO2 showed very little effect but the AZ40 and AZ41 with thinner layers showed interesting results.


However, this is not our field and we only have limited knowledge and equipment to evaluate the efficacy of our glassflake in Sun Screens.


We are interested to hear from either academic or commercial parties with knowledge in this area with the aim of progressing these findings further.


The tests for reflectance were conducted using a Croda TiO2 used in sunscreens versus the two types of titanium coated Glassflakes at the same addition level to try boost SPF level, see below:


Again it is interesting to see the differences between the materials and we reiterate that we are interested to hear from parties with knowledge in progressing this research work and these findings further.

Charles Watkinson
Research and Development Director at Glassflake Ltd | + posts