How to Turn a Matte Glaze Glossy with One Ingredient
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A simple way to turn your matte glaze glossy
Do you have a matte glaze that you wish was a bit glossier, or would you like a glossy version of one of your matte glazes? It’s really easy to convert a matte glaze to a glossy glaze, just by adding one ingredient – Silica (SiO2).
The 3 photos above are pairs of test tiles where the only difference between each pair is the addition of Silica.
Matte glaze on the left + Silica = glossy glaze on the right. Pretty cool, right?
To get more specific, let’s look at the recipes. These are screenshots from glazy.org
Calcium matte

Calcium gloss

A look at the recipes
The first thing to look at is the percentages for each material. The Whiting is the same, the Neph Sy is the same, the EPK is the same, the Frit is the same, but the Silica has 40 more grams (per 100g) in the glossy version than the matte version.
That’s literally the only change that was made to the matte glaze to make it glossy. So, if I were to make 100g of this matte glaze and then add 40g of Silica, I get a glossy glaze. And that’s exactly what I did to create the test tiles at the top of this article.
The next thing to notice is the recipe totals at the bottom. The matte glaze adds up to 100 and the glossy glaze adds up to 140. I could have normalized the glossy formula so that it also adds up to 100. This would re-calculate the totals for each ingredient to make them all a percentage of 100. But I left it this way to make the change obvious when I go back and look at it in the future.
A look at the chemistry
The following image shows the 2 glazes plotted on the Stull chart (named after the scientist who developed it in 1912). This chart takes the UMF of a glaze recipe and plots the Silica level (SiO2) on the x-axis and the Alumina level (Al2O3) on the y-axis. On the Stull chart, the only variables are Silica and Alumina. Fluxes and Boron remain constant throughout.
I have colour coded the regions of the chart to make it easier to see the patterns. The green region is where the matte glazes are found, the pink region is where the glossy glazes are found, and the yellow region is somewhere between matte and glossy. The turquoise regions are underfired.
Stull’s original research was done at cone 11, but I have re-created this chart by firing 50 tests with varying Silica and Alumina values at cone 6 and the patterns are generally the same. My tests also contained Boron, which is required to bring the melting temp down from cone 11 to cone 6. You can learn more about Stull’s chart and my cone 6 research here.

The white dots on the chart represent the Silica and Alumina levels of the matte glaze on the left and the glossy glaze on the right. As you can see, the matte glaze is plotted in the matte section of the chart and the glossy glaze is plotted in the glossy section of the chart. Make sense?
In order to understand where these points came from, let’s look at the recipes again. This time with the UMF included above the recipe. Check out the values for SiO2 and Al2O3.
Calcium matte

Calcium gloss

In both recipes, the Al2O3 is the same at 0.46. This makes sense because we didn’t change any of the ingredients that contain Al2O3. We only increased the Silica, which is pure SiO2.
In the matte glaze, the SiO2 is at 2.17. In the glossy glaze, the SiO2 is at 4.12.
More Silica added = higher SiO2. These highlighted UMF values are what I plotted on the Stull chart.
With Al2O3 levels being the same, the points are plotted on the same horizontal line because we are only changing the x-axis (SiO2) values. Anytime you add straight Silica to a recipe, you will move horizontally to the right on the Stull chart.
Another thing to look at in the UMF is where it says SiO2:Al2O3. This is the Silica:Alumina Ratio and it’s given as a numerical value that represents the number of Silica molecules for every Alumina molecule in the formula.
The matte glaze has a SiO2:Al2O3 ratio of 4.72. This means that for every molecule of Al2O3 in the glaze recipe, there are 4.72 molecules of SiO2. For the glossy glaze, the ratio is 8.98 molecules of SiO2 for every molecule of Al2O3. It’s this ratio that determines whether a glaze is likely to be matte or glossy. As the SiO2:Al2O3 ratio goes up, a glaze will move from matte to glossy.
But you can’t keep adding Silica forever. Adding Silica raises the melting temp of your glaze. Eventually the glaze will have too much Silica to melt and it will be underfired.
What you will generally find is:
SiO2:Al2O3 = 5 or less —> matte glaze
SiO2:Al2O3 = 5 to 6 —> “satin” glaze (between matte and glossy)
SiO2:Al2O3 = 6 to 12 —> glossy glaze
SiO2:Al2O3 = over 12 —> underfired glaze
Will adding Silica turn every matte glaze glossy?
No, not every matte glaze will turn glossy with the addition of Silica. As with everything in ceramics, there are some exceptions and nuances to be learned, but there’s a pretty simple criteria that will tell you if this method is likely to work.
All you have to do is take your matte glaze recipe and use glaze calculation software to look at the UMF (Unity Molecular Formula). My favourite way to do this is at glazy.org.
Create a free account first if you don’t have one, and then enter your matte glaze recipe. Glazy will convert your glaze recipe to UMF and also plot it on the Stull chart.
If your matte glaze falls into the matte region of the Stull chart, then you have what I call a “Stull Matte” glaze and this method of adding Silica is very likely to work.
How to adjust your “Stull Matte” glaze
All you have to do is add enough Silica to move the point on Stull to the right and into the glossy region.
You can do this by making a copy of your matte glaze in Glazy.org and then just use the + button to increase the Silica as you watch the dot move to the right across the Stull chart. Voila! You have re-formulated your matte glaze to be a glossy glaze.
If you want your matte glaze to be satin, or only slightly glossy, just add a small amount of Silica. This will move the dot only slightly to the right on the Stull chart. Typically a SiO2:Al2O3 ratio between 5 and 6 will give you a satin glaze. If it’s too matte, add some Silica. If it’s too glossy, remove some Silica. Testing is always required to get the exact result you’re looking for.
If you want it to be glossy, aim for a SiO2:Al2O3 ratio of between 7 and 10. Once your SiO2:Al2O3 ratio approaches 12, your glaze is at risk of becoming underfired.
If your glaze isn’t a “Stull Matte” glaze
If your matte glaze does NOT fall within the matte region of Stull, then adding Silica might not make it glossy. Some glazes are matte because they contain titanium, which crystallizes during the cooling cycle. Adding Silica to a titanium matte glaze won’t necessarily make it glossy. It might, it just depends how much titanium is in the recipe as well as where it falls on the Stull chart. Doesn’t hurt to try it.
Other glazes are matte because they’re underfired. An underfired glaze appears matte because it hasn’t melted into glass yet. Adding Silica to an underfired glaze definitely won’t make it glossy because adding Silica raises the melting temperature. If your matte glaze falls in the glossy region of Stull and does not contain titanium, there’s a good chance it’s underfired.
Look at the images below. The matte glazes are in the 1st photo. See how the glazes are slightly runny? And then the glossy glazes in the 2nd photo aren’t runny at all. This shows how increasing Silica raises the melting temperature of a glaze.


Make some tests and share your results
Always fire test tiles to be sure your new glaze looks the way you want it before making a large batch. And then fire some test pots before glazing all your work.
A really informative test would be to take a matte glaze and incrementally add Silica, moving slowly across the Stull chart, dipping a test tile after each addition. Then you will see the progression from matte to glossy and you can pick your favourite. I’d love to see your results!
If you have any questions, or want to share your results, please comment below or find me in my free Facebook community Understanding Glazes with Sue.
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Interesting and oh so simple. Would it work the other way – taking a glossy glaze and subtracting silica to make it more matte ?
Yes, it works the other way around as long as your glossy glaze contains pure silica as an ingredient. You can remove all the silica from your recipe and check the UMF and Stull chart to see whether it makes it into the matte section.
Some glossy glazes source all their silica from other materials like feldspar, frits, wollastonite, talc etc, and don’t contain pure silica as an ingredient. If this is the case, you can’t remove silica without removing fluxes, alumina or boron. Some ways of getting around this would be to replace wollastonite with whiting for example, since wollastonite contains calcium and silica but whiting only contains calcium. Then you’re getting into UMF calculations, which are fairly simple once you get the hang of it.
Thank you very much for uploading this.
My question is: I have a glaze that has no pure Silica in the recipe, can I add silica to it, and if so do I have to normalize the recipe to 100%.
Hi Ina, you can definitely add silica to a glaze with no pure silica. I would wait to normalize it to 100% until after you’ve tested it and decided the new recipe will work for you. It’s nice to keep the original recipe in tact when making changes so you can easily see the changes by comparing to the original.
Once you start using the new recipe and adding colourants, I would normalize it to 100% so the colourants are percentages of 100.
Of course, you could keep the added silica as an addition to the original recipe, just remember that you’d need to increase the amount of any colourants if you wanted them to be a percentage. So 3g of copper in a 115g glaze (for example) wouldn’t be 3%, it’d be 2.6%. I like viewing colourants as percentages of 100 because they’re easier to remember and compare.
Hi Sue,
The matte glazes are really runny, how can I make them just slightly less runny?
You would have to adjust the chemistry of the glaze recipe so that it melts at a higher temperature by either increasing the silica and alumina, or reducing the flux. If you’re not familiar with how to adjust the chemistry or your glaze, you could fire to a lower temperature, but that could possibly cause your clay to be under-fired. Or you could find different matte glazes that are made for your firing temperature.
I have a satin glaze but it fades off on dark clay bodies in all colors. Is it possible to adjust the glaze so that the color shows up on dark clay bodies?
Om4 Ball Clay 6 Colorants:
Talc 18 Buttercream Rutile 3
Gerstley Borate 22 Susan’s Sage Cobalt Carb 1, Rutile 6
Spodumene 36 The Blues Cobalt Carb 1.5
Tin Oxide 8 Golden Amber Rutile 2.5. Red Iron Oxide 2
Zircopax 10
Hi Susan, it’s hard to know what you mean by “fades off” and how I might fix it without a photo. And the recipe is a little jumbled here for me to read it. Are you in my Facebook group? If so, please post your recipe there with an image and tag me and I’d be happy to look at it for you.
Hi, I read, study, enjoy your publications.
BUT…
It is not clear what is the Cone or temp you fire, for example this matte to make it glossier. I will try… I fire at 04. Does it work with low temp ????}
Thanks!.
Hi Rosario, I fire to cone 6 but the chemistry works at all temps, including 04.
Hi I do not understand how relate the skull chart to my glaze recipe. Can you offer some insight. I am from Australia
Hi Sue, thank you so much for all yoru information, they are more than helpful. I am pretty new to the glaze mixing thing and have the following question. A friend gave me some of her self mixed glazes with the following recipe:
Custer Feldspat – 40%
Silica – 16%
Whitening – 16%
Ball Clay – 10%
Frittt 3124 – 9%
Talc – 9%
Addition: Brown Stain – 10% + Tin Oxide – 1%
The glaze looks beautiful, nice and matt, great coverage. I wanted to use the glaze for dinner plates and was worried that the glaze is too matte for the purpose, that’s when I found this page. I used the glazy.org Stull Matt and UMF info to figure out, how much Silica I need to add to make the glaze more glossy. I entered all the info and surprisingly the SiO2 is at 3.02and the SiO2:Al2O3 is at 9.99. So looking at the ratio figure (9.99), shouldn’t the glaze be rather glossy and not matte? I am a bit confused, sorry. Thank you.
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Hi Sue, thank you! Will be trying this on a matte glaze I’ve created from Ravenscrag.
Separate question – I’m wondering what oxide(s) made that soft pink/purple glaze that you have as one of your test tile examples. That colour has eluded me and I’d love to do some tests with my base glaze!
Hi Sue,
Your matte to glossy glaze transition is so clear. Would you please do the opposite, as well: show in detail how to shift a glossy glaze toward semi matte and matte?
Many thanks!