MANUFACTURING PROCESSES

Designing And Manufacturing In The UK, Since 1901.

WE ARE THE UK’S ONLY LARGE SCALE MANUFACTURER OF CERAMIC TILES.

Johnson Tiles is the UK's only large-scale manufacturer of ceramic tiles. Since 1901 we've been designing and making the finest selection of ceramic wall tiles, right here in the UK in the Potteries’ heartland of Stoke-on-Trent. Our growing portfolio of sustainable, British-made products is strengthened by complementary collections of porcelain and ceramic floor and wall tiles.

Our comprehensive portfolio of products has been used for interior and exterior design projects in homes, schools, universities, hotels, hospitals, commercial developments and leisure facilities across the world. Being a celebrated UK heritage brand is part of our culture, but the Johnson Tiles success story is built on innovation. With 120 years of experience, we are consistently raising the bar in terms of our inspirational design and manufacturing techniques, quality of service and sustainability leadership.

Our heritage in Stoke on Trent remains a strong element of our foundation, here we focus on each one of our manufacturing processes that take us from raw materials through to delivered product, and what is involved in each stage.

BODY PREPARATION

Body prep is the process of preparing the raw materials into a dust ready to be pressed into a tile. We receive over 40 deliveries of raw materials per week which are loaded into bays for storage. From here the...

BODY PREPARATION

Body prep is the process of preparing the raw materials into a dust ready to be pressed into a tile. We receive over 40 deliveries of raw materials per week which are loaded into bays for storage. From here the journey starts!

Tile Body Ingredients:

  • Ball Clay (Sourced from Dorset - 35%)
  • China Clay (Sourced from Devon - 19%)
  • Limestone (Sourced from Derbyshire - 9%)
  • Sand (Sourced from Cheshire - 17%)
  • Pitchers & Clay Scraps (20%)
  • Water

Our yard-man begins by loading the materials into hoppers. Weigh centres then weigh out the individual raw materials to our carefully calibrated recipe.

These materials are transported to the ball mill to combine with water to form slip. The mill contains two chambers which grind the mixture into very fine particles over the course of one and a half hours.

Once the slip leaves the mill, it is stored in underground arcs, each measuring 175,000 litres, before being pumped into the spray dryer.

The slip travels through a hollow lance which sprays the slip out at high pressure. Once the mixture hits the hot air inside the dryer, the heat (600°C input temperature) evaporates the moisture, and the remaining particles fall as dust.

The dust is then sent to silos where it is stored for up to 18 hours, allowing it to settle and homogenise. The dust is then ready for pressing.

PRESSING

Dust travels from silos into hoppers that are held above each press. Contained in these hoppers are probes which monitor the levels of dust and ensure that there is enough material to keep the presses going...

PRESSING

Dust travels from silos into hoppers that are held above each press. Contained in these hoppers are probes which monitor the levels of dust and ensure that there is enough material to keep the presses going. On average, four presses are running per shift, with different sizes pressed on each line.

The dust then travels into a homogeniser which spreads the dust evenly across the press, which is controlled by two proximity switches. The filler then moves forward, at which point, the dies drop down to allow the dust to fill the void. If there is any dust remaining in the grid, or abnormalities in the fill, the filler resolves this on the way back.

The cross beam then comes down, presses the dust into the cavities, forming the tile shape, before the cross beam ascends and the tiles are pushed out onto rollers. Tiles are pressed with the backstamp facing up, and are then flipped before they travel into the dryer. The dryer removes any additional moisture from the body, so the tiles leave the dryer with approx. 0.5% moisture at a temperature between 65 and 75 degrees, ready to be dipped.

GLAZE PRODUCTION

Frit and powder deliveries are received from Spain of a raw material mix, including glass, feldspar, clay and other raw materials. This frit is then dispensed into ball mills where the mix is combined with water...

GLAZE PRODUCTION

Frit and powder deliveries are received from Spain as a raw material mix, including glass, feldspar, clay and other materials. This frit is then dispensed into ball mills where the mix is combined with water.

Here, the mix is ground down by various media inside the ball mill to form a slop. The slop is then pumped out of the mills, sent to be sieved and is then sent through a magnet, to remove any large particles, impurities or metals.

The glaze is stored in tanks to ensure that the mixture can settle, removing any air, ensuring that the mix is in prime condition.

Engobe and glaze mixtures are both produced within this department. The engobe is applied to the tile prior to the glaze, and functions as a primer for the glaze, as well as working to combat thermal expansion while the tile is fired, thus creating a flat finished tile.

White glazes are then stored in tanks in glaze production, ready to be called off for dipping. However, if a coloured glaze is required, pigment needs to be added. Different colour powders create certain colour combinations, and each colour specification has to be carefully weighed by hand before being mixed into the glaze tanks to evenly distribute the pigment.

The coloured glaze is then sent for a sample run to be fired in the same conditions as the intended final product before returning to Glaze Production for a spectrometer test and a visual test. This establishes whether the glaze is in specification in terms of the colour mix.

If the glaze requires adjustment, the glaze department will add colour pigments accordingly and retest. If the glaze passes, then the glaze tank can be moved into a storage location, ready to be sent to the manufacturing plant.

DIPPING & DECORATION

Tiles exit the dryer at the optimum temperature to be sent down to the dipping lines. The tiles are first separated by policemen which ensure that the tiles are evenly spaced out as they travel down the line...

DIPPING & DECORATION

Tiles exit the dryer at the optimum temperature to be sent down to the dipping lines. The tiles are first separated by policemen which ensure that the tiles are evenly spaced out as they travel down the line.

Water spray is applied first to prepare the tiles for the application of engobe and glaze. The formulae for the engobes and glaze vary depending on the particular product in question, but must be carefully checked against batch information from Glaze Production. Glaze and engobe are both tested hourly to ensure they meet rigorous quality standards, including viscosity and density.

Once the engobe and glaze have both been applied, the tiles have all four sides scraped to remove any residual glaze, ensuring the tiles won’t stick together. A backwash is also applied to remove glaze from the backs of the tiles, which helps preserve rollers in the kiln for longer.

Any decorated tiles have additional processes which are applied. Options for decoration include rotocolour and Durst (inkjet application).

The rotocolour functions in a similar way to a paint roller. A texture is applied to the roller first via a laser; the glaze is then applied to the roller which evenly rolls over the tile to apply the texture.

Durst (inkjet application) works in a similar way to a printer, with a canvas uploaded to the machine, and this is then randomly printed onto the tiles.

After this decoration, the tiles pass through a Check Point which carefully assesses for any print errors or inconsistencies. This will then pull out any tiles that do not meet standards, to ensure they don’t reach the kiln. The tiles are then transferred to cages which store the product until it can be sent to the kilns for firing.

FIRING

Following on from dipping & decoration, the glazed tiles are stored in cages for a minimum of six hours before being sent to the kilns for firing. This helps to reduce the moisture content of the tiles, and...

FIRING

Following on from dipping & decoration, the glazed tiles are stored in cages for a minimum of six hours before being sent to the kilns for firing. This helps to reduce the moisture content of the tiles, and helps prevent explosions within the kilns.

To ensure that product is consistently being sent to the kilns for firing, and to maximise capacity, the TGVs (robots guided by sensors) are programmed each day to the schedule of firing for the kilns. The TGVs then retrieve product from the storage cages and bring them to the offloading bay at the kiln entrances.

Once the tiles have arrived at the kiln entrance, they are offloaded from the storage cages and are fed into the kiln. At the point at which the tiles enter the kiln, there are no burners on yet, with the kiln instead being heated by the exhaust at the rear end of the kiln. The entry heat is around 160°, with the temperature reaching around 600° before the tiles even reach the burners.

The tiles then steadily pass through the kiln according to the firing curve. The firing curve is a recipe which dictates the length of time of the firing and the temperature that the tiles are fired at. This is dependent on the size of the tiles, their thickness, and the glaze that has been applied. These firing curves are in-putted into the kiln computers by the RHFs (Roller Hearth Firemen). The firing curve then manages zones within the kiln, with each zone set to a specific temperature. Throughout the firing, the zone temperatures are measured to ensure they are sticking to the set point. The hottest temperature that the kiln can reach is around 1140°.

Once the tiles have passed through the full length of the kiln (around 105 metres for SL4 and SL5), the tiles pass into the cooling section of the kiln. This slowly cools the tiles down so that at the point of exiting the kiln, they are approx. 30°.

The RHFs carry out hourly checks to ensure that our fired products are within specification for curvature and thickness. The RHFs will check a full row of tiles from each kiln each hour to ensure they meet our stringent technical specifications. Once passed, the tiles then travel onto the feeding line to selection where they are checked prior to being packaged.

GLOST SELECTION

Once the tiles have left the kiln, they travel either directly onto the feeding line to selection, or into cages for storage, depending on the outstanding product that requires selection and packaging...

GLOST SELECTION

Once the tiles have left the kiln, they travel either directly onto the feeding line to selection, or into cages for storage, depending on the outstanding product that requires selection and packaging. The tiles are transferred onto the belt, either from the kiln exit or the storage cages, and then travel towards the Selection department.

The first stage of this process is the Vision machine. This machine is responsible for checking each and every tile that passes down the line to make sure it meets our standards. Depending on the size of the product that is passing down the line, the machine can check up to 70 tiles per minute. When the tiles have been passed by the Vision, they continue to travel along towards the line. They then reach the packing machine which folds the packaging around the tiles, wrapping them securely.

The packaged tiles then continue to travel towards the final stage on the line, which is where they are loaded onto a pallet. The packing machine functions automatically according to specific pallet configurations in-putted by the operative. Each hour the operatives on the line are also responsible for checking a box of each product as part of our Quality processes. If any faults are found at this stage, they are removed from the pallet, highlighted and registered to ensure our Process team can check these instances. Once the pallets are complete, they are then shrink wrapped in the Selection department, before being transported either to the CW1 or VNA warehouse.

LTK & FITTINGS

LTK (Low Temperature Kiln) & Fittings specialises in smaller bespoke pieces as well as supplementing general production with our standard small format sizes like 200x100mm, 100x100mm, and 300x100mm...

LTK & FITTINGS

LTK (Low Temperature Kiln) & Fittings specialises in smaller bespoke pieces as well as supplementing general production with our standard small format sizes like 200x100mm, 100x100mm, and 300x100mm.

The tiles are sent down the dipping lines, and glazing can take place either on biscuit or clay (biscuit has been fired, clay is pre-fired). The tiles travel down the line in a similar way to the standard dipping lines, but tend to travel at a much quicker pace.

Any specialist pieces must be hand sprayed in a booth, and these pieces are then loaded onto trays at the kiln entrance. This prevents small pieces from falling through the gaps in the kiln rollers. Tiles are then manually removed from the dipping lines before being transported to the kiln entry where they are fed into the kiln.

The kiln rotation takes about 45 minutes, depending on the product that is being fired. Once the tiles exit the kiln, they are manually selected by a member of staff. Each individual tile is checked for any blemishes or faults, and is removed if needed. All completed tiles are then packaged up before they are sent to the warehouse. All products that are produced in LTK & Fittings are sent to the VNA Warehouse.

WAREHOUSING

Between our two onsite warehouses (CW1 and VNA) we currently store over 29,000 pallets of tiles. Each week, we receive an average of 1,300 pallets from our manufacturing plants, and 400 pallets from...

WAREHOUSING

Between our two onsite warehouses (CW1 and VNA) we currently store over 29,000 pallets of tiles. Each week, we receive an average of 1,300 pallets from our manufacturing plants, and 400 pallets from our factored suppliers, with an average dispatch of 1,600 pallets a week. The warehouses work in partnership with our distribution haulier Bassett’s, to make sure that the most cost effective method of transport is achieved by utilising both consolidation and trailer fill. This is managed by the office teams in both warehouses.

CW1 is a bulk storage warehouse, which is where we store large rows of individual products. CW1 can store up to 10,000 pallets depending on space efficiency. All warehousing processes are carried out through the admin team transferring information from a paper picking system. The order picking process is completed using gas forklift trucks.

The VNA (Very Narrow Aisles) warehouse, also known as CW10, consists of 22 aisles of 11-metre-high racking, which can hold 16,000 pallets. Picking is done using Combi (‘K’) Trucks for full pallet picking and V12 (‘V’) trucks for part pallet picking. All warehousing processes in the VNA are carried out through the system, which means better traceability with different locations available for different products.

Let's Work Together

Our friendly and experienced team is here to help. If you’d like to get in touch, contact us via the email or telephone details below... Let’s Work Together.

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