Outgassing?

Conservation Issues

Outgassing?

Postby JohnMcafee » Thu Mar 10, 2011 11:43 am

I’m trying to figure out what is going on here.

Conventional wisdom would dictate that some kind of “leeching” takes place where the artwork has contact with acidic materials. However this twenty year old picture appears to be defying that convention.

The image is bonded to grayboard, probably with a spray adhesive, and the 'white' clouds in the picture are unpainted areas and were originally simply the colour of the paper.

Why is it that in the area where the paper is sandwiched tightly between two highly acidic materials there is no discolouration at all?
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Re: Outgassing?

Postby prospero » Thu Mar 10, 2011 12:07 pm

Had one very similar the other day. Maybe It's because the air can get to the paper just inside the window and not so much the part under the mount. Or maybe the light?
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Re: Outgassing?

Postby Keadyart » Thu Mar 10, 2011 12:11 pm

Direct sunlight damage??,Don't know John.(being exposed on the north coast would make anything or anyone look weather beaten)
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Re: Outgassing?

Postby Roboframer » Fri Mar 11, 2011 1:06 am

JohnMcafee wrote:Why is it that in the area where the paper is sandwiched tightly between two highly acidic materials there is no discolouration at all?


(Probably) because the acids are getting no help from UV light and, unfortunately, if you do not expose artwork to light .... you can't friggin' see it!

I've got a copy of The Times from my DOB - I mean an original copy (slate is pretty tough ya know) all pages are yellow, but they get less yellow towards the middle; regarding the centre of each page and the whole thing. Separate each page of today's paper and put them on a window ledge for just a couple of months and they'll be in worse condition.

If that exact same print had been matted and mounted with cotton artcare board, using starch paste etc hinges and glazed with 100% UV filtering glass/acrylic, you'd still see a contrast between the covered/exposed area, but without the acid burn from the mount's bevel.

If you want to see a print/painting in total pristine condition, look at it the very second it comes out of the printer/the artist signs it, otherwise, just like us human beans, it starts to die the second it is born, conceived even!

But we, as (born again) framers, can give things that must inevitably meet their maker, some quality of life in their short time on this planet .... Oh Yeah ..... lemee hear ya say it, lemee heeeeeeeeaaaar that you have seeeeeeeeeeeeeeeeeeeeeeen the light that has faaaaaaaaaaaaaaaaaaydid your pichtaaaaaas.

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Re: Outgassing?

Postby Nigel Nobody » Fri Mar 11, 2011 1:33 am

John,
The exposure to UV radiation and slightly higher temperature has undoubtedly contributed to the discolouration of the image that is exposed through the window in the mat.
The area that is hidden by the mat would be protected from UV radiation and insulated from heat to some extent, so it doesn't discolour at the same rate as the exposed area.
The very dark discolouration immediately next to the the mat bevel would not only be the result of UV radiation and heat, but would also affected by acid burn from the lignin's outgassing from the exposed core of the mat around the window.

Was there a barrier of any sort behind the paper? Was the back of the paper discoloured?

Acid and UV light are not the only negative influences on paper art, but are probably the most negative ones. Other things like sizing and brighteners used in the manufacture of the paper can also affect paper negatively, but it's difficult for framers to know any of those details and we can't change any of them.

It's my belief that we framers should attempt to minimise negative influences on paper art, by using the best quality conservation materials and methods available, where possible. Obviously the customer has a vital say in that.
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Re: Outgassing?

Postby prospero » Fri Mar 11, 2011 2:49 am

Good point Ormond re. paper quality.

I've seen watercolours that have been in contact with really nasty mounts for over 100 years and not a trace of discolouration. Good quality paper properly prepared.
It's a sad fact that some artists will paint on any old carp with no thought to the long term. It's probably a good rule of thumb that the worse the painting the higher the conservation aspects of the framing need to be.
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Re: Outgassing?

Postby Nigel Nobody » Fri Mar 11, 2011 4:16 am

It's true about some artists, Peter. I've had a 6ft x 3ft piece of newsprint painted on and that's had items like fish nets glued on and I'm expected to have a magic wand to cure it's problems and hang it flat. Sheeeesh!

The only way anyone could tell if there was no discolouration, in 100 years, would be to compare it with a twin piece, which had been kept in total darkness with an inert material protecting it both sides and with no atmosphere in the container. As that is unlikely I think it's a bit of a stretch to claim there has been no discolouration just from looking at it's present state.

There are probably many pieces which appear to be like new, but may have subtle differences in appearance, but more importantly, the physical state of the paper has also changed in the presence of lignin and many other chemicals in the framing materials and the paper itself. I'm not a scientist or a conservator, but I can understand that changes that are not obvious to our eyes do take place.

It's a bit like the seawater in my reef tank, that undergoes chemical changes all the time. I have to change 20% of it every week otherwise some of the chemicals like nitrates, nitrites, carbonate hardness, ammonia, calcium, phosphate, magnesium, copper, iodine and others, can build up dramatically and could wipe out the coral and the fish in a few months if there were no water changes. I can't see those changes, but I know they are happening and I can measure the most important ones with seven different test kits.

Measuring changes in paper, over time, could be done by paper/art conservators using appropriate testing equipment.
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Re: Outgassing?

Postby Not your average framer » Sat Mar 12, 2011 12:47 am

Perhaps whatever was used to bond the artwork to the greyboard has acted as a barrier or filter.

There are those who think that a coating of PVA glue between them can prevent acid migration between the greybaord and the artwork. While this is not a recognised practice these days, some degree of protection is likely to result from the PVA layer.

BTW, I'm not suggesting that we should follow this practice, it's just an illustration.
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Re: Outgassing?

Postby prospero » Sat Mar 12, 2011 1:02 am

I'm not a chemist, but I'm inclined to think that it is contact with the atmosphere that causes this more than UV light. An apple core will go brown even if you leave it in the dark.
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Re: Outgassing?

Postby Roboframer » Sat Mar 12, 2011 1:24 am

You have to peel the apple first - remove your lungs and expose them and see how they fare!
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Re: Outgassing?

Postby prospero » Sat Mar 12, 2011 2:04 am

My lungs are Ph neutral. (cough) :)
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Re: Outgassing?

Postby Not your average framer » Sat Mar 12, 2011 11:55 pm

It is interesting to note that grayboard causes less ranting, than MDF.

Sorry I'll get my coat! :oops:
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Re: Outgassing?

Postby Nigel Nobody » Sun Mar 13, 2011 12:57 am

Not your average framer wrote:It is interesting to note that grayboard causes less ranting, than MDF.

They get equal billing in my shop! ;) ;)
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Re: Outgassing?

Postby prospero » Sun Mar 13, 2011 2:35 am

Don't you like MDF then Ormond? :giggle:






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