Blister

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A raised, convex area or bubble on the surface of an object, often between adjoining layers of different material. (AICC n.d.) "Swelling on the surface usually caused by excessive heat or friction" (Jewett 1983). 
400px|thumb|right|Blisters in painting
==Related Terms==
blind cleavage; tenting
=== Synonyms in English ===
bubble; bulge
=== Translation ===
English 	blister
French 	ampoule
Spanish 	ampolla
Portuguese 	bolha
Italian 	bolla
German 	blase
Russian 	волдырь
Arabic 	نفطة
Chinese (Traditional)	浮凸
==Discussion==
Blisters can be found in a variety of media including paints, coatings, embedments, and metals (MFA 2013). Blistering can also be seen on stone monuments and sculpture (Vergès-Belmin 2008). Primary causes of blisters are fluctuations in or excessive exposure to heat and humidity, trapped pockets of air, liquid, or solvents, and insufficient adhesives. Soluble salts can contribute to blistering on stone.
Fluctuations in humidity induce supports to shrink, making them unable to accommodate the paint. As a result, the paint lifts away in long peaked blisters known as tenting. (Walsh 2014)
Additionally, the Canadian Conservation Institute notes that, "a blister may be a form of blind cleavage." (CCI 2013)
The Dutch Method is a treatment technique used when paint is blistering, flaking, or scaling on canvas. Damar resin is heated until dissolved, then mixed with beeswax. The warmed mixture (between 160-175 degrees F) is carefully brushed over the damaged area. The mixture chemically bonds with the paint and softens it, allowing the paint to be re-adhered with a heated palette knife. (Dorward 2014)
Consolidating the paint layer with a suitable adhesive, such as isinglass and honey, is another way to treat paint blisters. This substance can be injected into the blister, followed by warming of the area, and then resting the paint layer back down on its support. (Roberts 2014)
With any method, care needs to be taken not to shatter the fragile paint layer, remodel the paint, or change the artist's intention. (von Monschaw n.d.)
Small blisters in veneer can also be treated with heat. After protectively covering the area to be treated, a medium-hot iron can be pressed against the blister until flattened. Large blisters need to be slit first along the grain of the wood. Following the slit, the area is covered, heat is applied, and carpenter's glue is added if needed. As the blister flattens, any overlapping veneer is shaved off. Afterward, the flattened areas are weighted for 24 hours, then waxed and polished. (Consumers Guide 2006)
==References==
AICCM. "Blistering". Accessed 11 April 2014. Retrieved from http://www.aiccm.org.au/visual-glossary/blistering.
Canadian Conservation Institute. "Condition Reporting-Paintings. Part III: Glossary of Terms. Last modified 24 July 2013. Retrieved from http://www.cci-icc.gc.ca/publications/notes/10-11-eng.aspx.
Consumers Guide. How Stuff Works. "How to Repair Wooden Furniture Veneer." 12 April 2006. Retrieved from http://home.howstuffworks.com/home-improvement/home-diy/furniture-restoration/how-to-repair-wooden-furniture-veneer.
Dorward, Lisa. "Oil Painting Canvas Repair Techniques." Accessed 11 April 2014. Retrieved from http://www.ehow.com/info_8544819_oil-painting-canvas-repair-techniques.
Getty Research Institute. Art and Architecture Thesaurus online. "Blister" Accessed 11 April 2014. Retrieved from http://www.getty.edu/vow/AATFullDisplay?find=blister&logic=AND¬e=&english=N&prev_page=1&subjectid=300228340.
Museum of Fine Arts Boston. CAMEO. "Blister." Last modified July 24, 2013. Retrieved from http://cameo.mfa.org/wiki/Blister.
Roberts, Mark. "Structural Work." Accessed 11 April 2014. Retrieved from http://www.picturerestorer.co.uk/index.php?page=conservationandrestoration.
von Monschaw, Elline. Holy Cross Dundrum. "The Work of Conservation and Restoration." Accessed 11 April 2014. Retrieved from http://www.holycrossdundrum.org/index.php?option=com_content&view=article&id=34&Itemid=5.
Walsh, Valentine. "Paintings Ageing Gracefully or Grievous Bodily Harm?" Accessed 11 April 2014. 
Retrieved from http://valentinewalsh.co.uk/conservation/ageing/.
Vergès-Belmin, V., ed. 2008. Illustrated glossary on stone deterioration patterns. English-French ed., Monuments & Sites no. 15. Paris: ICOMOS and (ISCS) International Scientific Committee for Stone. http://www.icomos.org/publications/monuments_and_sites/15/pdf/Monuments_and_Sites_15_ISCS_Glossary_Stone.pdf 
Jewett, D. 1983. A glossary for recording the condition of an artifact. Ottawa : Canadian Heritage Information Network, National Museums of Canada. 
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