Stabilization of Breakage of Glass

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Conservation Treatments

All recommended treatments should be carried out after appropriate cleaning of the glass plate negatives.

Contents

[edit] Conservation Cases

[edit] Cracked Glass Plates

  • Cracked glass plates with intact emulsion can be placed emulsion side down on a piece of cardboard of the same size fixed by adhesive tapes along the edges.[1]
  • The cracked glass plate can be placed emulsion side up on a glass plate of the same format and the edges which got crossed by cracks fixed with adhesive tape to it (1/8" wide onto the emulsion side, e.g. 3M acrylic tape No. 850).[2] [3]

[edit] Broken Glass Plates

  • Broken glass plates can wrapped piece by piece in Silversafe paper and placed in an archival flap.[4]
  • There are different ways to build a conservation case for broken glass plate negatives:
    • Stabilization by an additional glass plate of the same size (or slightly bigger), fixation of the package by gelatinized paper along the edges[5]
    • For 3 to 4 pieces: place first piece (preferably one with a rectangular corner) emulsion side up on top of a second glass plate, fix it along the edges with adhesive tape (1/8" wide onto the emulsion side, e.g. 3M acrylic tape No. 850), proceed piece by piece (breaks across the edges should be over-taped along the glass plate edges)

Alternatively lines of breakage can be fixed by some spots of cyanoacrylate and the whole plate stabilized by an additional glass plate. Plates with more than 4 pieces: after fixing them in the described manner, additional covering by a second glass plate for stabilization.[6]

    • Broken pieces can be placed in a sandwich of cardboard (archival quality):[7]
      • Place the glass pieces in the right arrangement on a piece of cardboard, leave 1/4" between them ***redraw them
      • after removing of the pieces cut them out with bevel cut
      • place the pieces back, adhere them on the glass side with Filmoplast to the cardboard
      • additional piece of cardboard of the glass plate format for stabilization, fixation of the package by Filmoplast along the edges
      • another layer of cardboard fixed by a linen hinge along one edge is placed on top

Missing glass pieces can be filled by cardboard pieces, thin cotton swabs as a buffer between glass edge and cardboard


Disadvantage of glass sandwiches: glass sandwiched negatives get a pretty high weight and can go through fastened glass corrosion thus this method is only recommended for duplication not for long term storage.[8]

Disadvantage of using adhesive tapes: stabilization of fragments with adhesive tape can lead to unexpected changes by the tape if it lasts for a longer time[9]

[edit] Adhesive Sealing

Adhesive sealing rarely is an option since gluing is irreversible and few is known about the long term stability of most of the adhesives in use in connection with the silver image[10]

Demands on adhesives: refractive index similar to glass, weak viscosity (infiltration by capillary force should be possible), high polarity (to get a strong bonding to the very polar glass), high mechanical resistance, long term stability[11]

[edit] Adhesives in use

  • epoxy resins: irreversible, strong bonding, can evaporate deteriorating vapors , yellowing by UV-light and aging, oxidation at the surface by changes in temperature, hydrolysis if used with anhydride hardener (not with amine hardener) , little shrinking by drying

less yellowing than other epoxy resins: Ablebond 342-1, Epotek 301-2, HXTal-nyl 1, Araldite XW396/ 397, Eccobond 24 (after artificial aging: Ablebond 342-1 und HXTal-nyl 1 with the best mechanical stability)[12] [13] [14]

  • acrylic resins like Acryloid (Paraloid) B-72: weak bonding , good long term stability, solved in toluene long reversible[15] [16]
  • cyanoacrylates: for temporary use only since alkaline solutions on the glass surface can degrade cyanoacrylates[17]

===Recommended gluing technique===[18]

avoid direct contact between adhesive and emulsion since differences in tension can lead to lifting of the emulsion!

  1. Fixation of all pieces with adhesive tape on the glass side
  2. Vertical positioning of the glass plate
  3. Infiltration o the adhesive by a pipette (excess can be removed after one hour by a cotton swab with acetone in case of Acryloid (Paraloid) B-72)
  4. After one day the adhesive tape can be removed
  5. Horizontal resting of the plate for one week

Since glass is very hygroscope some molecules of water at the surface can interfere contact with the adhesive, so working in a dry atmosphere is recommended (also pre-treatment with silanes possible).[19]

[edit] References

  1. ? REMPEL, SIEGFRIED, 1987, p 88 et seqq.
  2. ? WEINSTEIN, ROBERT A.; BOOTH, LARRY, 1977, p 167 et seqq.
  3. ? GILLET et al., 1986
  4. ? REMPEL, SIEGFRIED, 1987, p 88 et seq.
  5. ? BÁLINT, FLESCH, 1995
  6. ? WEINSTEIN, ROBERT A.; BOOTH, LARRY, 1977, p 174
  7. ? REMPEL, SIEGFRIED, 1987, p 88 et seqq.
  8. ? BORTFELDT, MARIA, 2000
  9. ? NEWTON, ROY, 1989, 165-197
  10. ? BORTFELDT, MARIA, 2000
  11. ? GILLET et al., 1987
  12. ? CLARK, SUSIE, 1998
  13. ? GILLET et al., 1987
  14. ? NEWTON, ROY, 1989, 165-197
  15. ? CLARK, SUSIE, 1998
  16. ? GILLET et al., 1987
  17. ? NEWTON, ROY, 1989, 165-197
  18. ? GILLET et al., 1987
  19. ? NEWTON, ROY, 1989, 165-197
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