I needed some white gloss tiles 198mm wide (i.e. Johnsons sizing) and a bit= longer than 200mm, and happened to have some suitable in the shed, where t= hey had been stored for about 6 years stacked up on top of each other in pi= les of about 10. The tiles are white biscuit about 7mm thick. The shed is u= nheated but does not leak, although ventilation could be a bit poor. I was about to use them when I noticed they were all dished (i.e. bowed in = both directions) by 2 - 3 mm. I'm pretty sure they were not like that when = I used a few before. What a pain, so I need to source some more. Good job i= ts Johnson who have made the same ranges of tiles for years, all 2mm off th= e nominal sizes.
But I had no idea tiles did this. Perhaps they did not like temperature ext= remes. Anyone else seen this ? I should have stored them with a heavy weight on top !
it longer than 200mm, and happened to have some suitable in the shed, where= they had been stored for about 6 years stacked up on top of each other in = piles of about 10. The tiles are white biscuit about 7mm thick. The shed is= unheated but does not leak, although ventilation could be a bit poor.
n both directions) by 2 - 3 mm. I'm pretty sure they were not like that whe= n I used a few before. What a pain, so I need to source some more. Good job= its Johnson who have made the same ranges of tiles for years, all 2mm off = the nominal sizes.
bit longer than 200mm, and happened to have some suitable in the shed, whe= re they had been stored for about 6 years stacked up on top of each other i= n piles of about 10. The tiles are white biscuit about 7mm thick. The shed = is unheated but does not leak, although ventilation could be a bit poor.
in both directions) by 2 - 3 mm. I'm pretty sure they were not like that w= hen I used a few before. What a pain, so I need to source some more. Good j= ob its Johnson who have made the same ranges of tiles for years, all 2mm of= f the nominal sizes.
extremes. Anyone else seen this ?
I just checked the ones in the bathroom (I only used 2 where my tile spacin= g was slightly out and I needed some slightly taller ones) and they are fla= t. I'll put up a photo later on.
As everyone has said this is highly unusual behaviour in cermics regardless of the environmental conditions.
As long established manufacturers and importers with a reputation to protect Johnsons would presumably be intersted in investigating this matter themselves and giving you some sort of explanation. Or maybe just refunding you and keeping it to themselves.
Presumably as the size is unique there should be no possibilty of their questioning their origins. In other words I assume there are no counterfeits on the market.
If you carefully pack an example, along with a photograph of the stacks of other faulty tiles, and post it to them IMO there's no reason why they shouldn't replace them for you free of charge.
A link to some photos follows. Some show the warp more than others.
formatting link
perhaps 2mm max from flat, but they'd certainly look funny along the straight edge of a tile trim for example.
I've only get 20 or so tiles, so its probably not worth making a fuss about. It will be interesting to see how flat some newly sourced versions will be.
Its most likely a fault in manufacture which you didn't notice at the time. Apparently the odd warped tile isn't that uncommon. Or put another way its a lot easier to put a warp into a tile prior to firing than it is to bend it afterwards. Ceramics can be porous so that they crack with frost, but they don't distort.
The fact that you didn't check them at the time is irrelevant as you knew you were dealing with a trusted supplier and so saw no need to examine them closely before storing them.
You could always send some pictures - maybe if you photographed two together back to back, bending away from each other, as with picture no 3 but with two together that might show the fault even better. And tell them how many faulty ones you have. It's only the price of a first class stamp.
longer than 200mm, and happened to have some suitable in the shed, where they had been stored for about 6 years stacked up on top of each other in piles of about 10. The tiles are white biscuit about 7mm thick. The shed is unheated but does not leak, although ventilation could be a bit poor.
both directions) by 2 - 3 mm. I'm pretty sure they were not like that when I used a few before. What a pain, so I need to source some more. Good job its Johnson who have made the same ranges of tiles for years, all 2mm off the nominal sizes.
extremes. Anyone else seen this ?
bring em indoors and let them dry out over a week or so.
bit longer than 200mm, and happened to have some suitable in the shed, whe= re they had been stored for about 6 years stacked up on top of each other i= n piles of about 10. The tiles are white biscuit about 7mm thick. The shed = is unheated but does not leak, although ventilation could be a bit poor.
in both directions) by 2 - 3 mm. I'm pretty sure they were not like that w= hen I used a few before. What a pain, so I need to source some more. Good j= ob its Johnson who have made the same ranges of tiles for years, all 2mm of= f the nominal sizes.
extremes. Anyone else seen this ?
I will do that and let the panel know. But I'll have to get on with the job so I'll try and get hold of some local= ly. I only need 5 or 6 for a window sill.
a bit longer than 200mm, and happened to have some suitable in the shed, w= here they had been stored for about 6 years stacked up on top of each other= in piles of about 10. The tiles are white biscuit about 7mm thick. The she= d is unheated but does not leak, although ventilation could be a bit poor.
ed in both directions) by 2 - 3 mm. I'm pretty sure they were not like that= when I used a few before. What a pain, so I need to source some more. Good= job its Johnson who have made the same ranges of tiles for years, all 2mm = off the nominal sizes.
re extremes. Anyone else seen this ?
ing was slightly out and I needed some slightly taller ones) and they are f= lat.
There is variation in tile size. Some tiles can be bought in sizes which vary slightly from the normal size.. I can't imagine them bending after manufacture. So they must be defective.
But having seen the pictures and they are dished to the finished (glazed, waterproof) side it could well be damp into the back (unglazed, porous) side causeing a differential expansion. Be interesting to see if they do flatten after a few weeks/months inside.
I have a load of wall tiles stored in the loft ATM, not as damp as a shed but not as dry as a heated house...
longer than 200mm, and happened to have some suitable in the shed, where they had been stored for about 6 years stacked up on top of each other in piles of about 10. The tiles are white biscuit about 7mm thick. The shed is unheated but does not leak, although ventilation could be a bit poor.
both directions) by 2 - 3 mm. I'm pretty sure they were not like that when I used a few before. What a pain, so I need to source some more. Good job its Johnson who have made the same ranges of tiles for years, all 2mm off the nominal sizes.
extremes. Anyone else seen this ?
+1, although there's no certainty it will be successful. Very gentle heating in a domestic oven set at just over 100C may speed it up. However, even if the dishing can be removed by drying out, either slowly or with gentle heat, then it will re-occur, particularly in a moist environment such as a bathroom, and the tiles will have to be replaced. Better to ditch them now.
Moisture expansion is a well known phenomenon with porous ceramic materials, notable earthenware tableware and porous tiles. Over time, moisture is absorbed through unglazed surfaces causing the body of the plate or tile to expand. The glaze on the surface doesn't expand, so is put under tension and eventually will crack. Old earthenware plates typically show a pattern of fine cracks over the surface, known as 'crazing', due to this process. A tile is only glazed on one side, so is likely to 'dish' as the body expands but the glaze doesn't (think bi-metallic strip), although eventually the strength of the glaze will be exceeded and it will craze. The problem is related to the porosity of the item, amongst other things. The lower the porosity, the less the problem, so vitreous tableware (porcelain, bone china etc), sanitaryware* and vitreous tiles seldom if ever suffer this fault.
Most earthenware and tile manufacturers are well aware of this problem, and usually take steps in the manufacturing process (composition, firing temperature etc) to minimise the effect. The fact that the OP has tiles that have dished suggests something was not right in their manufacture.
Googling for 'moisture expansion' & 'delayed crazing' brings up a lot of references, but most are rather technical and not really very helpful.
Whether or not the manufacturers would be prepared to replace them after all this time, I've no idea, but the OP has nothing to lose by trying.
*but not always. Many years ago a well-known UK sanitaryware manufacturer had problems with one of their kilns under-firing. The consequences were that after several years of use, certain items that went through that kiln would fail spectacularly, sometimes with quite a bang as a crack several mm wide suddenly opened up across the item. A sort of delayed-action time bomb!
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