Ceramic Tableware: What is On-Glaze, In-Glaze and Under-Glaze?

If you’re a supplier of tableware, you want to make sure your products are not just of high quality, but are decorated with unique designs to stand out in the marketplace. 

One way to achieve this is by using decals; a decal is a type of transfer application that is utilised to apply pre-printed images or patterns to a specific product. 

However, decals for ceramic tableware can be created with a variety of different pigments, and each type has its own unique benefits and drawbacks.It is important to understand the differences before you make a purchase. 

In this blog post, we will discuss the three most common types: on-glaze, in-glaze and under-glaze. 

What is a Glaze?

Before we break down into the three types of decal, you’ll need to know what “glaze” actually is. 

To put it simply, glaze is a smooth, glassy surface that is adhered to the ceramic body as a necessary component of ceramic tableware. 

Some experts think that glaze originated from the “ceramic clothes” used for decoration on ceramics, which is to say, the coating applied by ancient pottery in accordance with the rough surface, easy water absorption, and other criteria. 

This is an additional layer or coating that makes stoneware or porcelain waterproof and suitable for holding liquids. 

Glazes also allow a variety of on-glaze, in-glaze, or under-glaze surface treatments, including glossy or matte finishes.

What is On-Glaze?

On-glaze decals are the most common type of transfers as they are fired at the lowest temperature and have the widest colour range. 

During the decorative process, the design is first printed on a special paper that is pre-coated with water soluble glue, then soaked in water. 

On-glaze ceramics are produced by applying the decal paper directly to the glazed surface and then firing at 700-850°C. 

As the firing temperature does not reach the melting temperature of the glaze layer, the design stays on the ceramic surface and cannot sink into the glaze layer. 

What is In-Glaze?

The firing temperature for an in-glaze decal is higher than that of an on-glaze decal. It reaches the melting temperature of the glaze on the ceramic product. 

Firstly the raw clay is fired to a bisque state. Following this firing the ceramic piece is dipped or sprayed with glaze and fired to around 1100 degrees (glost temperature). The ceramic piece is then sealed in a shiny surface.

After this firing , the design is applied to the glazed surface.  The decal is then fired 1050-1100°C, which enables the transfer to sink into the glaze as the glaze surface is again reaching melt temperature.

Firing at these temperatures ensures excellent wear-resistance, durability and rich colours. In addition to this, when touching the surface of the product there will be a more homogenised feel. 

What is Under-Glaze?

This kind of twice fired ceramic decal provides ultimate durability. 

The decal is placed on the bisque state ceramic piece and hardened through firing at 800 degrees,  the glaze layer is added followed by a final firing to fully seal the decal at around 1100.

The pattern is concealed by a transparent glaze film after firing, and the surface is bright, glossy and smooth.  

The most prominent feature of under-glaze is that the colour is perfectly preserved and lasts a long time and thus durability is 100%. 

Wrapping Up

We hope that this blog post has helped to clear up any confusion you may have had about on-glaze, in-glaze and under-glaze decals for ceramic tableware. 

As you can see, each type of glaze has its own set of benefits and drawbacks, so it is important to choose the right one for your needs. 

If you have any further questions, please feel free to contact us and we will be happy to help. 

In the meantime, take a look at our ceramic decal service here.

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