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Glass Discussion & Research. NO IDENTIFICATION REQUESTS here please. => British & Irish Glass => Topic started by: terrierman on April 06, 2007, 08:03:39 PM

Title: Annealing Cracks
Post by: terrierman on April 06, 2007, 08:03:39 PM
Hello Everyone

I'm probably showing my lack of knowledge here but never mind. I keep seeing attractive Monart pieces with 'annealing cracks', some of which I have bought. They may have full genuine labels. I have always assumed that many of  these flaws occurred during manufacture, as a result of uneven cooling or whatever. Then I ask myself if that was the case how did these pieces ever come to be sold. Was there a market for Monart 'seconds', or were trivial defects in fact ignored? Or have all these defects only appeared after sale?

Any thoughts would be welcome.

John



Title: Re: Annealing Cracks
Post by: Frank on April 06, 2007, 08:59:48 PM
These were a feature of the poor annealing of Monart and are almost a feature of it. I must admit I don't know if they were considered seconds. But do they affect value... certainly for some and for others not. Michael Parkington never bought damaged glass... UNTIL, he started collecting Monart. The first damaged piece was a decanter with a set of glasses, this had a single annealing crack within the pontil. The set is shown in Ysart Glass Plate 40. He lived with it for two weeks but it troubled him to much and I bought it back. It then got bought by an equally fastidious collector and they kept it for a month before selling it back... its now in the Perth Museum.

Next I had a remarkable piece absolutely covered in annealing cracks, literally thousands of them. Parkington 'borrowed' it as he was fascinated by the effect and after a few weeks decided he had to own it. It must have been in the auction but I cannot see it in the catalogue. Thereafter one or two other damaged pieces of unusual style were accepted with annealing cracks. For example powder boxes with stress cracks under the knob of the lid... very common! All of the other damaged pieces in the Parkington sale were caused after his death.

An alternative view can be found in Dominic's article:

Quote
http://www.ysartglass.com/Ysart/DominicP.htm

One way to build up a good and inexpensive collection is to buy examples with annealing cracks. These remain relatively cheap, and after all were commonplace during production runs; they are not the result of post-production abuse or accident. These are very display-able and enable the collector to amass a big collection cheaply.

My personal attitude is that it depends entirely on the piece, if the piece is particularly unusual or of especial beauty then no damage would concern me. This will be tested soon as I plan to offer the powder box in plate 21 of Ysart Glass for sale shortly. It has the under-the-knob stress crack but is a non catalogue almost unique item as described in Ysart Glass.

It will of course be interesting to hear other views too  :)
Title: Re: Annealing Cracks
Post by: terrierman on April 06, 2007, 10:08:16 PM
Frank -  You make a very interesting observation here, that poor annealing is almost a feature of Monart. The quote from Dominic supports this and really encapsulates the reason for the question. He accepts that annealing cracks were commonplace in production runs, which is what I have always believed. I am still puzzled as to how these items came to be sold as 'perfect', if that is the case. From my very limited knowledge, the impression which I have of Salvador Ysart, or Paul for that matter, is that he was fiercely proud of his abilities and would not have taken kindly to flawed examples of his work being retailed, in fact I suspect that he might well have destroyed such pieces. I suppose he probably did not see the glass once it went to be labelled and packed for dispatch. Did the cracks develop then?
Or is it only now that small flaws such as these are regarded as significant? In which case the premium on perfection seems less than reasonable because, if it was good enough for the maker then surely it should be good enough for us. The anecdotes which you give concerning Parkington really confirm your own view that the degree of imperfection which is acceptable must ultimately be a decision for the buyer based on the rarity and appeal of the item. In any case that is the logic of the market place I suppose.
It would be interesting to hear the thoughts of glassmakers on this question.

John



Title: Re: Annealing Cracks
Post by: Frank on April 07, 2007, 08:57:28 AM
It was Paul Ysart not Salvador that was the perfectionist as far as glas quality was concerned. Salvador was a lot more pragmattic and I would not be at all surprised to learn that he actively ignored minor annealing cracks. You have to remember that the Monart range was the only glass being produced in this style at Moncrieff and that their technology department had a steep learning curve to address the issue, that it still occured in the 1960's when the retired Frank Eissner attempted making paperweigghts on Saturdays, most failed in annealling - although this was due to him only having access to the firms MS1 metal, the Monart metal was strictly for the Ysart's. We know for certain that it was the company chemist that attempted to develop the techniques for Monart Cameo and that nearly every attempt with the shades ended in shattered failure. So clearly there was a fundamental technical flaw in the understanding of annealling.

Yet if you contrast Monart and Vasart the problem seemed to disappear and we have detailed accounts of the Vasart annealling lehr, being little more than a heated corrugated iron tunnel with the glass being carried on metal milk crates... as a new crate was pushed in, all the crates would move alog and the front one could be removed. Perhaps it was pure luck it worked so well. Perhaps the attempts to resolve the problem at Moncrieff were to 'clever' and we can continue to speculate that because Monart was only in sporadic production, that the lack of continuous working made resolving the problems to difficult... or not cost effective.

Salvador clearly disapproved of Paul's attempts to make paperweights 'gift ware baubles' and at Vasart he was equally pragmatic about their production being low end. The company was always in a difficult financial state and the luxury of greater quality certainly had to be taken into account. Moncrieffs were also financially challenged from the 30's onward and would have needed to take care of expenses - Monart was a very expensive glass to produce and production had to take second place to normal production.
Title: Re: Annealing Cracks
Post by: KevinH on April 07, 2007, 10:27:12 PM
There are quite a lot of known paperweights with annealing cracks, some with a large number of such faults. This applies to both early Vasart items and early Paul Ysart pieces.

Apart from small annealing cracks in the base of a weight, it would seem that the majority of the flaws occur much later in the life of the item, otherwise they would surely have been unsaleable, either from the works or later via other outlets.

I suspect that there are lots of early Ysart / Vasart weights that still hold stresses just waiting for the right conditions to be released as a crack - or worse! Maybe it is much the same with the art glass, or would the vast difference in thickness of a vase etc, compared to a paperweight, make a real differrence to stress retention?
Title: Re: Annealing Cracks
Post by: Frank on April 08, 2007, 09:46:31 AM
More modern glass is subject to a lot more measured technology, COE's of the glass and any colourants being carefully matched and annealing being very accurately managed. Also mould blown glass is more carefully controlled.

With any free-blown glass, regardless of COE as soon as you create layers of glass there will always be some stresses created due to the different temperature at the time they are joined. While annealing eases these it is unlikely to remove them completely.

Stresses that remain, in Monart, without causing the 'hallmark' stress cracks can result in cracking later as a reaction to a knock or even fresh heat induced stress releasing the original stress destructively. Many collectors have lost pieces of Monart that had NO stress cracks as a result of:
  • Resting a cigar in an ashtray
  • Immersing in warm water
  • Subjecting to 'frost' level teperatures
  • Displaying in partial direct sunlight
  • Displaying in an illuminated cabinet with 'hot' light source (LED bulbs resolve this)
  • Displaying in a cabinet without possibility of air-movement (Air holes needed top and bottom)

    • An interesting difference between annealing cracks and post-retail stress relief cracks is that the former tend to be stable and the latter unstable. The instability results in cracks that are long and irregularly shaped and can grow, even to the extent of splitting the piece into two pieces. If you notice a stress relief crack appearing it is important to keep an eye on it for change, if it grows over a few weeks, you need to get the glass treated quickly. Especial care being taken while transporting to the restorer as the temperature changes and vibration of the journey could exacerbate things. The treatment consists of drilling tiny holes just ahead of each end of the crack, the crack will continue to grow until it reaches the holes but will be stable thereafter.

    If you have a piece that does split it is worth getting it repaired simply because of the rarity of Monart glass.
    Title: Re: Annealing Cracks
    Post by: nigel benson on April 08, 2007, 01:51:02 PM
    Hmm,

    Having just skipped through all the above I find it difficult to agree with how 'annealing crack' is being defined.

    Whilst it may be that there are cracks in Monart are due to poor annealing, it seems to me that any cracks that occur after production should not be referred to as annealing cracks. If travelling an item to retailer meant that an inherent fault in that item was revealed then it is more than likely it is was as result of that poor annealing - as may also be the case when something is impacted at a later date - however, it is a fine line as to what caused the damage. Without the vibration, or the impact, either item might have stayed in perfect condition.

    There is a problem in accepting all cracks as either original annealing cracks, or, as linked to poor annealing, since it means that any crack could be passed off as 'original'. If we accept that original annealing cracks do not grow (which I fundamentally disagree with) then this would also give the unscupulous licence to sell under a false banner.
     
    I agree that the value of a damaged item is in the eye of the beholder, however my experience as a dealer in Monart is that buyers are always put off by any damage, whether perceived as original, or more obviously from later treatment.

    My advice to collectors has always been to buy if you like the item and if you don't hope for an increase in value. My advice to investors, or collector's with an eye for investment is, do not buy damaged items - however that damage may have occured. Experience of re-sale on damaged items - especially at auction - is that such items do not do well. Of course there are always exceptions, but as a rule-of-thumb, this statement is true.

    I own damaged items because I get enjoyment from them aesthetically and/or because they are rare. Luckily, most display in such a way as to avoid the damage!

    I have, in the past taken cracked Monart to restorers. None have come up with a fulproof way of repairing cracks (or in other glass for that matter), which is why as a dealer I avoid damage, but as a collector I may entertain it. I am amazed at the idea of drilling holes into Monart. Might not the vibration, or any heat induced by the drilling, actually make the crack grow? With the imperfections and inherent stresses in the glass might not the crack even bypass the holes drilled successfully by the restorer? The concept sounds somewhat Heath-Robinson, not to say drastic, to me. Does it adhere to Museum practice? If not, it may well be one to be avoided. Perhaps taking rudimentary care of storage and display (as you suggest Frank) might be a better course of action.

    Nigel

     
    Title: Re: Annealing Cracks
    Post by: Frank on April 08, 2007, 03:10:52 PM
    Quote from: nigel benson on April 08, 2007, 01:51:02 PM
    it seems to me that any cracks that occur after production should not be referred to as annealing cracks.
    Agreed! My term "post-retail stress relief cracks" was not quite correct, it should be "post-manufacture stress relief crack damage".


    Quote from: nigel benson on April 08, 2007, 01:51:02 PM
    Might not the vibration, or any heat induced by the drilling, actually make the crack grow? With the imperfections and inherent stresses in the glass might not the crack even bypass the holes drilled successfully by the restorer? The concept sounds somewhat Heath-Robinson, not to say drastic, to me. Does it adhere to Museum practice?

    Done with the right equipment and technique this is not an issue, I had Wilkinson's do a repair to a Monart lamp base with cracks at the rim and it was them that told me about this technique. So certainly museum practise.  I have done it myself on very old mirrors with cracked original glass, it is not that hard to do. It just requires patience, but there is a slight risk of causing more damage. I would certainly use a professional restorer for non-flat glass.  It is not H-R but good materials science, a crack extends from its tip never from a smooth edge and that is what the drilling does. The object can still expand and contract with temperature changes but the effect of the hole is provide a release for the forces at the tip of the extending crack. The tricky part is placing the hole, you have to predict where the crack will travel over say 5mm - attempting to drill on the end of the crack itself will probably result in disaster. If I had a piece with a growing crack, I would rather use that method of repair than wait for the eventual separation of the piece!
    Title: Re: Annealing Cracks
    Post by: millarart on April 11, 2007, 05:32:31 PM
    .

    . It has the under-the-knob stress crack but is a non catalogue almost unique item as described in Ysart Glass.

    It will of course be interesting to hear other views too  :)

    oh Frank that sounds painful :o :o :o :o :o :o :o ;D
    Title: Re: Annealing Cracks
    Post by: karelm on April 13, 2007, 07:27:55 PM
    I have (un)fortunately a lot of time on my hands so read a lot of what is posted on this board in all topics.  I believe this is one of the most informative I have read.  I have a couple of specific thoughts on this topic that I will post in due course in "paperweights".
    Please archive this thread when it has run its full course!!
    Kind regards,
    Title: Re: Annealing Cracks
    Post by: nigel benson on April 15, 2007, 05:50:46 PM
    Hello,

    To take this idea of drilling holes to stop a crack continuing to its conclusion, it would seem that if I own a piece of Monart (or other glass for that matter), which has a number of cracks in it, the answer is to drill 5mm holes at either end of all of them (or at least the ones chosen as 'at risk') - thus producing an item that would be more suited as an impliment in the kitchen to strain the veg's? I seriously think not!

    Just because a reputable restorer, such as Wilkinson's, suggested this invasive practice as a means of repair, it does not imply that it is indeed Museum practice. I would go further and suggest that this method of "repair" is a hang-over from the days when staples were used to put together either ceramic or glass items. The item in question would be drilled on both sides of the crack (or break), at intervals, and a staple inserted to hold the vessel together. It is frowned upon by museums - and was long ago left behind as a means of repair. Nowadays, any repairs untaken in a museum have to be reversable for a whole range of reasons.

    The idea that drilling holes in an item as a repair is also a misnomer in my opinion. I can see that putting something back together is a repair, but scarring it with holes............?

    It maybe that in certain circumstances that this method might be considered as a means of curtailing a crack, however I think that I would rather let time take its course as I would find the holes in an item frustratingly irritating.

    Nigel
    Title: Re: Annealing Cracks
    Post by: Frank on April 15, 2007, 06:54:21 PM
    More like an 0.05 mm hole Nigel, but that is only of use if there is a crack AND that crack is unstable... i.e. still growing.

    I don't have a problem with such a soution, if it was suggested to me by a competent restorer as the only way to retain a single item rather than two partial items, I know which I would choose ;D

     >:D Two pieces and put one on eBay >:D
    Title: Re: Annealing Cracks
    Post by: taylog1 on April 15, 2007, 07:58:52 PM
    The principle is no different to ships and planes having rounded corners on doors and windows (the original Comet had square windows, which caused all the problems). By drilling the hole, when the crack reaches it the aggregated stresses are spread out over a wider area, and so the forces are less at any given point. One should then be able to fill the hole in (with light sensitive superglue for example) to make it less apparent if you wanted to.   

    [J.E.Gordon - The new science of strong materials - is an enlightening read, and has a chapter on cracks in glass. It helps explain why cracks become unstable as they grow, the stresses are proportional to the length of the crack, but concentrate on the ends. Greater stress equiates to greater propensity to grow.]   


    One of the references I came across referred to using a flat computer screen and a polarised filter to look for signs of stress in a piece of glass (in this instance a telescope reflector blank).  http://www.usm.uni-muenchen.de/people/cries/christoph/schleifseite_eng.html
    I've just tried it with a camera polarising filter (common on the non digital SLRs) and the screen is definitely polarised.   
    If anyone's got a piece of internally stressed glass and a polarising filter on their camera I for one would be very interested in the result - the principle's sound, but is the effect big enough to show up on camera ?

    taylog1


    (and on an entirely different matter, in looking for a reference above I came across this site, which I found interesting. Apols if referenced elsewhere. http://www.glassblower.info/glossary.html)
    Title: Re: Annealing Cracks
    Post by: nigel benson on April 20, 2007, 09:53:23 AM
    Hiya,

    I've just been mopping any awfully large 'egg-on-face' off my brow :-[

    My apologies Frank - goodness knows where I got the idea that the holes would be that large. All I can say is that Sunday was a rough old day for me, so I went onto the GMB for a bit of light relief - only to get that wrong!! Shouldn't have got up that day I don't think. Ho hum.....

    As for the comments I made about stapling and whether or not it was a museum approved method of repair, they stand.

    I fully understand the principle behind the idea, but comparing an industrial solution to use on a piece of art glass does not seem to be comparing like with like.

    If I relate this solution to whether or not to have damage, such as a chip, taken out of a rim and I find it difficult to to accept one, but not the other, since both are interferance in some way of the items original condition.

    Ultimately "you pays yer money and ya takes ya chioce". 

    Nigel
    Title: Re: Annealing Cracks
    Post by: Frank on April 22, 2007, 03:50:22 PM
    No need for the egg Nigel, a hole is a hole :)

    I will be eBay testing the impact of a biggish stress crack on an unusual piece of Monart, later tonight.
    Title: Re: Annealing Cracks
    Post by: Frank on April 23, 2007, 05:19:08 PM
    I have added the powder box to the catalogue on Scotland's Glass so you can get get a good look at the crack.

    Link (http://www.scotlandsglass.co.uk/cms/index.php?page=shop.product_details&category_id=195&flypage=shop.flypage&product_id=1591&option=com_virtuemart&Itemid=1)

    Due to the extra thickness of glass, the stress cracks under Monart handles are usually very different to those found on the surfaces of vases and the only difference to a crack caused by a knock is that it only affects one-layer.
    Title: Re: Annealing Cracks
    Post by: Frank on May 08, 2008, 02:29:45 PM
    An interesting aside with staple repairs, god museums can be stuffy, is that they were not intended to repair an object of desire but to continue the useful life of an object. The technique is often described in early books of household repairs. For museums to discount social history contained in objects is of course ridiculous. It is a pity that today we (in the West) consider it better to throw away damaged pieces of household stuff and buy new ones - a trend that needs reversing to help combat the damage to our environment caused by excess consumption. There is a nice trade in repairs of household items, including disposable lighters, carried on on the sides of streets throughout India and presumably most countries where the cost of living means that impressing the neighbours is of lesser importance.