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Mystery and Wonder of Gutskin

A museum conservator recently said,

“Gutskin is a material whose time has come.”   

She meant, those of us who are tasked with the preservation and treatment of cultural heritage made of internal mammal tissues understand precious little about the material and the time is ripe for us to put in a concerted effort to know more.  Graduate students at New York University and the UCLA Getty conservation programs have recently raised questions about gutskin artifacts they were seeking to treat.  Staff installing Smithsonian collections in new Arctic Studies Center exhibits in Anchorage, Alaska have found the identification of tissues on several artifacts quite perplexing.  Alaska State Museum has been pondering the unique properties of this material and its treatment as well.

Shown is a gallery of some intriguing artifacts in the Alaska State Museum collection.  Click on the image to enlarge.

Horelick Gutskin Repair Testing

Lauren Horelick, Mellon Fellow at the Smithsonian’s National Museum of the American Indian, is investigating repair techniques for ethnographic gutskin.  Please consider filling out her SURVEY and take a peek at her research proposal:

Expanded gut research outline/ list of research questions. 

Research goals:

  1. Condition issues affecting inner skin materials in museum collections, and past treatment choices.

Look at past reports, objects (treated and untreated) in collections at NMAI and NMNH (possibly others AMNH, Penn Museum) to get a sense of how pervasive certain condition issues are (if applicable).

  1. Survey conservators to see what materials are favored for repairs and why. Is there any re-evaluation of how these past materials have fared over time with handling, exhibition, travel, storage etc. 
  2. Lit review of chosen/popular materials to determine composition, and see if their formulations have changed, what are long-term aging properties, availability in other countries (differing trade names?).
  3. How applicable are tests and mends made with hog casings (success or failure of the use of this material). How similar/ dissimilar is hog casing to marine mammals intestines.
  4. Assess penetration and/ or material interaction of select adhesives used in conservation repair. What layers of the inner skin are affected, how does the adhesive interact with the collagen, does the adhesive disperse evenly or does it create a sharp perimeter. What are the effects of adhesives applied while gut is wet versus dry- does this effect success of mends. Observation of gut when wet and dry. Are mends made with dampened raw gut and dampened hog casing preferable to mends applied via adhesive. Is adhesion created due to van der Waals (dispersion forces) or hydrogen bonding. How strong are these mended materials, and what is left behind on the inner skin if/ when the adhesive is reversed. What are the optimal properties of the adhesive when applied to gut.

Acquisition of vouchered sample material.

  1. Vouchered sample materials primarily from artists Fran Reed (who worked with innerskins) are in Kelly McHugh’s possession, and are available in moderate/small sizes for analysis. Research will focus on only summer tanned intestines of seal and hog casing.
  2. The acquisition of vouchered, unprocessed samples from a selection of no more than two arctic marine mammals commonly used in Arctic Native objects, such as seal(ringed, ribbon or harbor),or walrus will require permits. This may not be necessary at this phase of the study, as many materials are already in possession. However, if permits and travel are approved, the acquisition of unprocessed material would aid in examining the soft mucosa of tissue cited in the ethnographic literature as removed.

Characterization of inner skins: Work with MCI

Observation of the layers of inner skin (front and back) before treatment.

Framework of question: The layered and physical structure of gut relate to its biological function of one-directional permeability (outward flow of nutrients through the gut). This property of one-directional permeability was exploited for use in water proof garments, such as parkas. How do these specialized interior and exterior tissues (submucosa, and muscularis externa)[1] appear with SEM. According to Hickman (1987:8) the gut wall contains capillaries that close up upon the death of the animal. Are these features visually distinct, and can they be characterized. Are they different from animal to animal. Study by Linn (2008 unpublished) demonstrated difficulty in characterization of intestines with PLM, therefore use of SEM will yield better quality images, which may aid in characterizing and describing features. Winter versus summer tanned materials examined for pH, and strength measurements. How does gut physically change from dry to wet states.

Why characterize gut: The understanding of the structure of both sides of gut will aid in interpreting how conservation applied materials are interacting with the substrate. Sample material used in mockup’s will not be from an object, and from the macro perspective it’s difficult to assess which side relates to the submucossa or muscularis externa, therefore mock-ups should reflect how conservation materials are applied to the gut.  The incorporation of hog gut is for comparative purposes aiding in assessment of compatibility between materials. Knowledge of how pH, and strength influence or interact with adhesives may be necessary for meaningful analysis and interpretation.

Proposal For Phase 1 Testing: Observation of inside and outside layers of gut with SEM.

Proposal for Phase 2 Testing: Testing penetration of various adhesives on inner skin materials.

Framework of question: Is it necessary to apply adhesives when damp gut creates a bond with itself. Dialogues with Native skin sewers revealed a concern for the long-term stability of conservation applied mends with adhesives. At present there is no prior research as to how adhesives interact with gut. The goals of the study will aim to clarify this, and determine if their application is necessary if stable mends can be made with using only water dampened hog casing.

Goal: To understand membrane properties to be able to select repair method that works compatibly with material. Is it possible that the raw gut is the most compatible.

Step 1: Research/ determine a staining medium that won’t separate from selected adhesives. The stain chosen should be distinguishable with SEM elemental mapping to track the penetration of the adhesive Adhesives chosen will number no more than three and will be determined based on results of conservation survey. Figure out how best to prepare and observe adhesives-treated inner skin samples for analysis with SEM.

Step 2: Adhesives will be applied to one side of the hog casing, and one side of the seal to eliminate variables. The side the adhesives are applied to should be the submucosa (or interior-food side of the gut).

Literature review:

  1. Sources within conservation that describe the condition and treatments of inner skin materials- results, trends, overlooked aspects ( such as consultation with cultural groups, attitudes about sewing versus adhesives) use of lubricants, pros and cons of differing adhesives.
  2. Studies with SEM on inner skins within conservation, mammalogy, material science, microscopy to see how samples were prepared, results of studies, and possible identification of constituent parts of inner skins.
  3. Characterization of inner skins to identify constituent layers, chemistry, morphology and physical characteristics in conservation, mammalogy and other sources- is there overlap or variation in terminology.
  4. Cultural use: focus  will be on gut skin parkas and will be limited to one particular culture. Examination of inner skins use for survival, commerce, ceremony, subsistence….etc. Cultural use, cleaning, care, and attitudes about how non-Native people care for parkas.
  5. Compile annotated bibliography.


How are inner skins influenced by the addition of foreign materials; where are the adhesives going, and does application influence final appearance, aging properties, pH, and strength. Do modern adhesives compromise long-term care of the objects, if so why, if not why?

[1] L.Morrison (1986) describes the structure of gut and the various layers present after Native processing, stating that the soft mucosa are removed leaving tough submucosa and muscularis externa. Muscularis externa is divided into two layers; an inner one containing fiber bundles in a circular arrangement, the outer in a longitudinal direction parallel to the gut wall.