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L3954N - Cone 10 Engobe for H550

Modified: 2024-09-02 04:28:23

White

Notes

Both Zircopax and Black Stain are shown as additions. Use one or the other (to get white or black).

This recipe the product of a series of tests where the percentage of nepheline syenite was progressively reduced (from 25% originally) to reduce the firing shrinkage to match H550 (it is important that engobes shrink the same as the body or they will flake or crack off during firing or later during ware use). Amazingly only 10% nepheline syenite is needed to make this fit Plainsman H450, H550. Again, do not use this recipe on porcelains (e.g. P700) or whitewares (e.g. H570, P600), the recipe needs more nepheline for them (to increase firing shrinkage, we have another recipe, L3954J that does this).

This creates very plastic slurry so it sticks well to leather hard clay (because of the high percentage of ball clay). If you do not have this brand name of ball clay then substitute another.

The Zircopax version fires quite white, leave it out completely if that is too white. If on thick enough this will block and body speckling, glazes will react as if on porcelain.

As an engobe this works best when mixed as a thixotropic slurry. Please follow the instructions for the cone 6 version at the L3954B page at the Plainsman Clays website.

Related Information

Transparent and RavenTalc silky matte glazes on black engobe at cone 10R

Clay is Plainsman H450. The L3954N black engobe was applied at leather hard stage (on the insides and partway down the outside). The G1947U clear glossy glaze over it on the inside produces a deep and vibrant hue (left). The inside glaze on the right is GR10-C Ravenscrag silky matte. The outsides are GR10-J Ravenscrag Dolomite matte with a little added cobalt and iron (for blue and brown).

Two G2571A Bamboo versions: With iron, rutile-zircopax

These mugs are Plainsman H450 fired at cone 10R. Both have a black engobe (L3954N) applied to the insides and half way down the outside during leather hard stage (the insides are glazed with Ravenscrag silky matte and G1947U over the black engobe). The bamboo glazes can thus be seen over the black (upper half) and the raw buff body (lower). The bamboo glaze on the left has 1% iron added to the base G2571A recipe. The one on the right has 3.5% powdered rutile and 10% zircopax added.

Can an engobe block manganese speckle at cone 6?

Yes. If it is a true engobe. This is L3954B fired at cone 6 on Plainsman M340S, it is fire-shrinkage-fitted to this clay body and opacified with Zircopax. The cover glaze is G2926B transparent. The opacity that this engobe is able to achieve here is because it is vitrifying to the same degree as the body, no melting is occurring and that is why it is completely opaque (even though it is applied as a very thin layer at the leather hard stage). This same performance could be expected in reduction firings to block the iron speckle (using the L3954N and variations recipes).

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