Magnified Movements - Using Eulerian Video Magnification with Cultural Heritage Objects

This project was begun in September 2014 and has gone through multiple phases.  Our ultimate objective is to be able to monitor sensitive, complex objects, such as illuminated manuscripts or modern mixed media works. As a practical matter we began with small samples of more simple materials that we subjected to fluctuations in RH.  In this section we will describe efforts to establish methods that worked for us.

Humidity Chambers

Humidity Chamber 1

Chamber1

A type of humidity chamber like that often used in conservation treatment.

  • 16″ x 24″ x3″ Molded fiberglass tray
  • Wet blotters lined the bottom of the tray
  • Light fixture diffuser cut to fit the tray, separated the wet blotters from the object
  • Nylon screening used to soften the texture of the diffuser
  • Hollytex® non-woven polyester to give a smooth surface
  • Digital hygrometer
  • Acrylic sheeting to cover tray
  • Strip of battery powered LED lights
ADVANTAGES DISADVANTAGES
Easily constructed and taken apart. Moving samples from one RH to another was awkward and we were not able to accomplish it quickly
 Materials readily available The size of the LED strips that would fit into the tray did not give strong enough light
It was not possible to get the lights far enough from the sample to get even raking light
Filming through the acrylic glazing did not give enough clarity to produce good results with the magnification filter (comparison of glazings can be found below)

 

Humidity Chamber 2

Chamber2

A chamber was fashioned from purchased plastic utility shelves. This was an attempt to build something quick, using materials already available in the lab to enable us to set a protocol for filming.

  • 36 x 72 x 18″ five shelf, plastic ventilated storage unit; middle shelf used for chamber
  • Insets of Davey® board (book board) cut to fit upper and lower shelf, covered with polyethylene sheeting and placed to cover ventilation holes
  • Ethafoam® blocks cut to support Museum Glass® to fit on one of the longer side wall
  • Acrylic sheeting cut to fill gap next to Museum Glass®, held in place with duct tape
  • Smaller side covered with acrylic sheeting door; hinged with duct tape
  • Side opposite Museum Glass® window covered with Mylar held in place with duct tape
  • Last side covered with Mylar® door, held in place with duct tape, sealed at bottom and sides with magnetic strips
ADVANTAGES DISADVANTAGES
Extra storage space conveniently located Awkward moving objects in and out of chamber
Cheap, quick to build Duct tape was not reliable, needed frequent repairs
Convenient height for filming Door hinged with duct tape fell off
Good lighting possible
Good resolution through Museum Glass®
Small leaks easily repaired with duct tape

Humidity Chamber 3

Designed with inexpensive, easily available materials.

  • 1/2″ PVC pipe
  • PVC three-way elbow fittings
  • Linen tape used to create handles
  • Museum Glass® fitted into Ethafoam® blocks sealing front of box
  • Door created on right side using Mylar® attached at top with double stick tape and secured closed with flexible magnetic strips
  • Last two sides of box covered with Mylar®, double stick tape and insulating foam where needed
  • Two interchangeable lids, on acrylic sheeting and one diffuser with Techwipe® stitched to panel
  • Strips of Volara used to seal bottom where box rests on board
  • Foam insulation used to seal gaps created by size difference in pipe and corners
ADVANTAGES DISADVANTAGES
Good seal held for at least 96 hours Needs to be handled carefully
Relatively lightweight A little large to be easily stored
Easy to change out silica gel sachets, sponges, blotters
Good resolution through Museum Glass®

Glazings

Filming samples in Humidity chamber 1 gave unexpectedly poor results; we saw no movement in any of the paper samples in the chamber.  We determined that the acrylic sheeting was obscuring enough detail to prevent the magnification filter from working.  We tested various types of glazing collected as samples over the years for image clarity.  The quality of the image was determined with visual observation and we did not run each test through the magnification filter.

Samples tested are listed as the samples were labeled:

AntiReflective Laminated Glass Optimum Museum Acrylic Tru Guard Museum Glass UV filtering acrylic
Conservation Clear Acrylic Optimum Museum Glass Tru Vue AR Reflection Control Lexan™
Conservation Reflection Control Static Shield Acrylic Tru Vue Museum Glass Borosilicate glass
Optimum Acrylic Tru Guard Conservation Clear Tru Vue Ultra Clear Borosilicate glass

Several people judged videos and all agreed that TruVue Museum Glass® gave the best quality image,
closely followed by Lexan.  The images below are stills taken from videos shot with no glazing and through three types of glazing:

No Glaze Lexan™ Tru Vue Museum Glass Optimum Acrylic
No Glaze Lexan TrueVue Museum Glass Optimum Acrylic

 

We did not run these tests through the magnification filter because the test shots were only a few seconds long for each glazing.  In another test later on we did see movement on a sample filmed through acrylic sheeting.  We suspect that the problem with the first sheet may have been that it had multiple, minor scratches.

Lighting

We tested many lighting sources and angles.  Ultimately we found that a strong, consistent raking light is the most useful.  The angle and direction of the light source is best selected for each individual object.

 

Light Source Advantages Disadvantages
Photo Floods Strong, even light source Cannot be left on for long periods of time
Battery Powered LED Light Strips Convenient Do not give consistent light over long periods of time
LED Flashlights Convenient, can be arranged into various configurations easily Do not give consistent light over long periods of time
300W Work Lamp Cheap, convenient, clip on so placement is versatile Very hot
Incandescent Track Lighting Convenient, happen to be in the lab, consistent light source Limited range of adjustment without climbing ladders
Task Lamp with Incandescent and Fluorescent Lamps Convenient Not strong enough
Scandals® (banks of fluorescent lamps) We happen to have them Do not get good strong shadows from fluorescent light.
Ambient Fluorescent We happen to have them Do not get good strong shadows from fluorescent light.
Fotodiox LED 312DS Bi-color Even, consistent light; can control color temperature between 3200K and 5600K; relatively affordable Must be relatively close to the object

 

Controlling Relative Humidity

METHODS USED: Ultrasonic mister, Wet blotters, and Silica gel in canisters

Silica gel in canisters or sachets proved to be the only controllable method as opening and closing the chamber is necessary.

Sample Materials Tested

We have tested many materials, but have only posted videos where there were visible results.  We will be happy to respond to questions about the materials we tested that are not posted in the videos.

Glassine Silver gelatin photographs
Lens tissue Mounted Woodburytype
Whatman #1 Modern papyrus with gouache
Various Japanese tissues Linen fabric
Various handmade papers Leather
Various mouldmade papers Vellum
Various machine-made papers Wooden boards with alum-tawed thongs and leather fragments, probably 17th C.