Underglaze, In-Glaze or On-Glaze: Where the Decoration Sits Decides Everything

The Problem: The Same Logo Behaves Differently Depending on Where It Is

The artwork is identical on two mugs. On one, the logo still looks right after three years of commercial washing; on the other it is worn at the edge by year two. The difference is not the print method or the ink — it is where the decoration sits in relation to the glaze. That single decision is the most consequential one in a mug specification, and it is often never discussed.

Products in this guide: Japanese Long Rectangular Ceramic Serving Plate · Japanese Style Ceramic Ramen Bowl

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The Three Positions

Underglaze — the decoration sits under the glaze. The design is applied to the unfired or once-fired body, then covered by glaze and fired. The glaze becomes a physical layer between the decoration and everything else: cutlery, detergent, the drink. This is the most durable position, and the safest from a food-contact standpoint, because the surface touching food is plain glaze.

Its cost: the glaze slightly softens and diffuses the image, so fine detail and sharp small type are harder. Colour range is also narrower, because the decoration must survive the glaze firing.

In-glaze — the decoration is fired into the glaze layer. The design bonds into the glaze rather than sitting beneath or above it. It is a middle position: better durability than on-glaze, better definition than underglaze, and the widest practical balance of colour and wear.

On-glaze — the decoration sits on top of the fired glaze. Applied as a decal and fired at a lower temperature, it offers the widest colour range and the only practical route to gold, platinum and other metallic effects. Its trade-off is the obvious one: the decoration is the outermost surface, directly exposed to the cutlery, the rack and the scrubbing.

What Each Position Means in Service

What Each Position Means in Service

• Durability under commercial washing — highest underglaze, high in-glaze, lowest on-glaze.
• Fine detail and small type — softened underglaze, good in-glaze, sharpest on-glaze.
• Metallic and brightest colour range — not possible underglaze, limited in-glaze, available on-glaze.
• The food-contact surface — plain glaze underglaze; glaze with bonded decoration in-glaze; decoration on the surface on-glaze.
• Relative cost — higher underglaze because of rejects, mid in-glaze, lower on-glaze.

Reliability note: the qualitative ordering above reflects how each position behaves in service. Exact cycle counts should always come from a test on your item and decoration, not from a category name.

Choosing, and What to Write Down

Choose by the wash regime and the role of the logo. A branded mug in a café that runs a commercial washer daily belongs underglaze or in-glaze. A gift item where colour fidelity and gold trim carry the value is a legitimate on-glaze use — provided the care instructions say so.

If a metallic is required, accept the constraint. Gold and platinum are on-glaze by nature. The specification should therefore state the wash limitation explicitly rather than implying the durability of a fired decoration.

Write the position into the specification. "Decoration beneath the glaze" and "decoration on the glaze surface" are different products; a quotation that does not name the position is not comparable with one that does.

Ask for the durability test on the actual item. Wash cycles against the real decoration, with the regime stated, is the only way to convert the choice into a number.

For the related decisions — durability testing, colour approval and compliance documents — see <a href="https://www.storiwareceramicmugs.com/oid1757203/The-Custom-Mug-Programme-Buyer-Guides-by-Decision.htm">the custom mug programme guides</a>. Our <a href="https://www.storiwareceramicmugs.com/products2147420/Custom-Ceramic-Mugs-Cups.htm">ceramic mugs and cups</a> range can be specified with the decoration position stated per item, and the <a href="https://www.storiwareceramicmugs.com/oid1756307/Custom-Ceramic-Mugs-Bulk-Order-Factory-Direct-from-China.htm">bulk order programme</a> explains how decoration, sampling and testing fit together. To match a decoration position to your use, <a href="/contact-us.htm">send the artwork and the wash regime</a>.

The spec freeze guide explains how artwork and packing files are locked between orders.

What to Put in the Order

• The decoration position stated per item, not implied.
• The durability test result on the actual item and decoration, with the regime.
• The care instruction that matches the position chosen.
• The colour implication accepted — narrower range underglaze, metallics only on-glaze.
• The food-contact statement for the surface that touches the drink.
• The same-position comparison when comparing two suppliers.

The packaging guide explains how retail-ready and protective layers are specified together.

The Habit That Ties It Together

The habit is to ask where the decoration sits before asking what it costs. Buyers who do this stop replacing mugs for a reason nobody wrote down.