Sieve Residue Test for Tile Slip and Glaze

Sieve Residue Test for Tile Slip and Glaze

Sieve residue is one of the simplest checks in a tile plant, but we should not treat it as a small lab formality. It tells us how much coarse material is still remaining above a selected sieve size after grinding or preparation.

In tile production we mainly use this test for body slip, glaze slip and sometimes spray dried powder control. If the residue suddenly changes, we have to look at the mill, screen, raw material preparation, glaze grinding or spray dryer feed condition before it becomes a production defect.

What sieve residue means

In this test we pass a known quantity of slip or powder through a selected sieve. The material retained on the sieve is called residue. The result is normally reported as a percentage of the original sample.

If the residue is high, it means more coarse particles are present. If the residue is low, it means the material has passed more completely through that sieve. But we should remember one important point. Sieve residue is not the full particle size distribution. It only tells us what is retained above that sieve opening.

Why residue matters in tile production

Grinding fineness affects tile behaviour. In the tile books, grinding is connected with vitrification, firing shrinkage and porosity. Sintering is not controlled by grinding alone. Body chemistry, bulk density and firing temperature also matter. But grinding residue is still one of the practical plant checks we can use every day.

When residue is not controlled, we may see different production troubles:

• coarse particles remaining in body slip after milling
• screen blockage or screen damage at the mill outlet
• poor control of spray dryer feed slip
• coarse particles entering glaze, engobe or application lines
• visible specks, line marks or application disturbance when coarse contamination reaches the surface

So the residue test is not only a lab number. It is a quick signal about grinding, screening and material movement through the plant.

Common sieve sizes used for slip control

For tile slip control, the production control reference uses residue checks at 63 micron or 45 micron. The exact sieve used depends on the plant standard, product type and the control system already fixed in that factory.

We should avoid changing sieve size casually. If one shift checks on 63 micron and another shift checks on 45 micron, the numbers will not have the same meaning. The plant should mention the sieve size clearly in the lab record.

Where we check residue in the plant

There are a few practical points where residue control is useful.

1. Body slip after wet grinding

After wet grinding, we check whether the slip has reached the required fineness. The production control reference mentions checking residue at 63 micron or 45 micron, with control by every mill load. This is useful because each mill load can vary due to raw material condition, water addition, grinding time, mill charge and deflocculation behaviour.

2. Mill outlet screening

In continuous mill systems, the outlet slip can pass through screens. The tile process reference explains that coarse solids can be separated first, then finer screening can be used before the slip goes forward for spray drying. Residue from screening can be returned to the mill.

This is why a damaged sieve or wrong screen handling can create trouble. If coarse material escapes the screen, the lab residue may increase and the downstream process also becomes less stable.

3. Spray dried powder check

For spray dried powder, the production control chapter mentions sieve analysis on dried powder using screens in the 600 to 125 micron range, with daily control on an average sample. This is a different control from 45 or 63 micron slip residue. We should not mix both results in one line without mentioning the test method.

4. Glaze and engobe preparation

Glaze and engobe also need screening before application. In the glazing line, screens and magnetic separation help protect the application system. If coarse material, agglomerates or contamination enters the glaze line, it can disturb application and create surface problems.

For glaze, the residue value should be connected with the plant's own glaze preparation standard. A floor tile glaze, wall tile glaze, engobe and digital-compatible glaze preparation may not follow the same residue target.

How we should record the residue test

A residue result is useful only when the record is complete. We should write:

• sample name or mill number
• sample point, such as mill outlet, storage tank, spray dryer feed or glaze tank
• sieve opening, such as 63 micron or 45 micron
• wet or dry method used
• sample quantity used by the plant method
• residue percentage
• operator name, time and shift
• action taken if residue is outside control

Without these details, the number becomes weak. A residue value without sieve size or sample point cannot help us troubleshoot properly.

What to check when residue is high

When residue goes above the plant control limit, we should not adjust blindly. First we have to find where the coarse fraction is coming from.

• Check whether the mill grinding time or continuous mill condition has changed.
• Check mill charge, raw material lumps and hard material variation.
• Check whether the screen is torn, blinded or wrongly fitted.
• Check whether residue return to the mill is working properly.
• Check slip density and viscosity because poor flow can affect screening.
• For glaze, check grinding, tank agitation, screen condition and contamination.

Many times the residue result is only the symptom. The root cause may be in grinding, raw material preparation, screen maintenance or slip handling.

What sieve residue cannot tell us

Sieve residue cannot tell the full particle size distribution. Two slips may show similar residue on 63 micron, but their finer particle distribution may still be different. That difference can affect rheology, pressing behaviour, firing behaviour and glaze application.

So we should use residue as a routine plant control test, not as a complete particle size study. For deeper investigation, we need a separate particle size distribution method or a more detailed sieve analysis depending on the material and lab facility.

Practical conclusion

Sieve residue is useful because it is fast, low cost and easy to repeat in the plant lab. For tile body slip, we commonly control residue at 63 micron or 45 micron as per plant standard. For spray dried powder, we use a different sieve analysis range. For glaze and engobe, residue control protects application quality and surface finish.

The main point is simple. Always mention the sieve size, sample point and method. Then only the residue number has meaning. If we track it properly, it becomes a good early warning for grinding and screening problems.

I hope I have provided enough information about the sieve residue test in tile production. If you want to know anything more or share your plant practice, please share it below in the comment section.