Crazing, a mark of age?

Do all old mugs have crazing? Most all of mine do except for this Trader Vic's Seahorse-shaped mug I just got.

It's dark blue so I don't know if I just can't see it or there isn't any.

(old people seem to all have crazing!)

Crazing is basically cracks in the glaze. it is often, but not always, a sign of age. It can occur in new mugs if the glaze does not "fit" the clay. Ceramic clay is like stone, and glaze is more like glass. These can have different expansion rates, and if exposed to sudden tempeture changes, crazing can occur. If it is in an old piece, well, that is the way it goes. If it is in a "new" mug, that is bad.

From the glossary at digitalfire.com :

"(Crazing) is caused by a mismatch in the thermal expansions of glaze and body. A glaze of higher expansion shrinks more than the clay to which it is attached and therefore crazes."

My observations: The majority of my Tiki mugs don't seem to have crazing. Neither does the rest of my too many pieces of ceramic/pottery. What crazing is present is mostly in translucent glazes.

Crazing is often attributed to age but it can occur immediately after the firing and it's not always present even in very old pieces.

Although Tiki mugs were probably manufactured as throw away pieces I don't think the crazing is a sign of poor craftsmanship. A lot of the big name art pottery has crazing in it.

(I sound like an echo, but apparently Tiki King and I were posting at the same time.)

[ Edited by: woofmutt on 2002-09-25 10:27 ]

On 2002-09-25 10:01, Tiki King wrote:
Crazing is basically cracks in the glaze...Ceramic clay is like stone, and glaze is more like glass.

So then should we assume that if there is crazing, then there are possible "leaks" from the impurities of the the ceramic that can get into your drink? This kind of goes back to the thread of "mug safety/lead tests" (http://www.tikicentral.com/viewtopic.php?topic=1078&forum=5), which included the following info (courtesy of TikiKing): So the once properly glazed piece is now a poorly glazed piece and should be treated as a decorative piece only? Is it possible that by using crazed mugs we are weakening the structure of the ceramic? Kind of like using a paper bathroom cup day in and day out and eventually having it collapse. Am I way off on this? Am I rambling? Is my fez on too tight? Tell me! TELL ME!!!...Hey, where did everybody go?

SugarCaddyDaddy

In this fast-paced, hectic, crazy world that I participate in, Tiki is my center-of-calm that brings me back to where I can slow down, relax, have a drink, chat with friends and just be me.

[ Edited by: sugarcaddydaddy on 2002-09-25 10:38 ]

voice o experience
don't put anything you like in the dishwasher.
no, i didnt wreck any mugs ~ just a really cool pink and black pottery/lazysusan thing. crazed the finish. wierd though, as time has passed, the crazing looks less. must have been the infusion of water..and heat..

I saw on the "Antique Roadshow", or one of those shows, a while back that certain ceramic dealers (not Tiki mug) have a method to craze a new peice to make it appear older. Like they heat it up and quench it or something. Thus increasing the value.
Al

A word about crazing. Crazing is considered bad by those who don't like it. Those who do like it call it "crackles" glaze. Tiki-King is partly right about its cause, but the conditions that made the glaze not fit were during the firing. Cracks that appear later were already weak spots.
I see a lot of slip cast pieces with a white liner glaze go crackly after a few uses because the owner didn't read the warning about dishwasher or microwave use. Crazing should still be 100% functional and will leach neither more nor less impurities or chems than a stable glaze. However, they should not be used in the microwave or dishwasher since the crazing can allow small amounts of water to become trapped. If it were to be suddenly heated up to gaseous state, then BOOM! SO... sugarcaddydaddy, Keep on using your mugs without fear, but don't microwave them and they'll last longer.
BTW, just because the glaze looks like "good glass" doesn't mean it's foodsafe. However, no responsible ceramist would be using lead on dinnerware these days.
Crazing=bad, Crackles=good. same thing really.

Sometimes crazing is a desired effect caused by double-firing...The Japanese especially prize this technique for their ceramic dinnerware...you'll often see it on bowls and sake sets. Grey

Bump -

So does anyone drink from heavily crazed vintage mugs on a regular basis?

Do you feel as though you'll only live once, so what the heck?

I know there is a possibility of lead leaching, do you think it increases if you were to, say, drink hot coffee from a vintage crazed mug every day?

Maybe stick to new?

Bamboo Ben was crazed long before he got old.

There are PLENTY of newer mugs to drink from, so save the older crazed mugs to look at.The more you handle the old mugs, the more of chance to dropping 'em, or chipping 'em or whatever, and then you have to wash them as well....

I sometime wash and 'christen' a vintage mug before it goes into retirement from active duty, but I've recently had some queries from a new member that wants to drink from one.

I know there are a few people who regularly slurp from oldies, but I play it safe like you grog, and drink from the modern ones primarily.

I drink out of vintage (and crazed) mugs once in a while, though not every day. Part of it is the "you only live once" attitude. Something's going to kill me. It might as well be lead out of a tiki mug, though I doubt that would be it. Still, it's better than getting hit by a car in the crosswalk while walking to work.

I've seen a little about lead exposure in ceramics, before. From my understanding, you're not exposed to a serious amount of lead in occasional uses-- like that leaded crystal that only gets used once a year, even if you put something alcoholic in it. Now if you used that leaded crystal every day for several years, even with non-alcoholic stuff, you might have more cause for concern. I don't believe any info exists about how much lead is leached from a ceramic vessel per drink, and how that might correlate to lead poisoning, but I'd be careful about using anything day after day.

Most of my Mai-Tai consumption is from a double rocks glass that I was able to lift from the Royal Hawaiian on my last visit. (It's no tiki mug, but it feels so cool while watching syndicated episodes of Five-0 on the TV.) Anyway, the point I was on the way to making is that since I'm using old ceramics rarely, I tend to worry about it even less. The air pollution outside is probably more hazardous.