My aim is to provide a complete, reasonably priced, and rugged microfade tester (MFT) and comprehensive personalised training to allow Conservators to immediately apply the technique to their institution's display requirements.
OPTIONS
I provide two reasonably priced microfade testers (MFTs); one based on an LED lamp and the other filtered xenon. The prices (below) include:
I provide two reasonably priced microfade testers (MFTs); one based on an LED lamp and the other filtered xenon. The prices (below) include:
- all hardware including a dedicated MFT minicomputer and pre-loaded software.
- one-on-one video-conference assistance with setup and use - including spectrometer and MFT specific software.
- fully set up Windows11 microcomputer or laptop
- assistance with all aspects of practical microfade testing including interpretation of data, reporting, the strengths and uncertainties of accelerated light ageing, and its application to individual institutions’ display environments and exposure guidelines.
- comprehensive video and written instructions.
PRICES
Depending on client choices and component costs at the time of purchase:
LED lamp option: ~USD16,000 (including training)
Xenon lamp option: ~USD 25,000 (including training)
Depending on client choices and component costs at the time of purchase:
LED lamp option: ~USD16,000 (including training)
Xenon lamp option: ~USD 25,000 (including training)
LED vs XENON
The results of a survey of over 230 colourants tested using both sources show that for routine lightfastness screening - where colourant responses are rated against those of the ISO Blue Wool Fading Standards – the two illuminants deliver very similar results. In some cases there are differences, most likely where the valley between the excitation and fluorescence regions of the LED spectrum overlaps activity spectra of particular colourants and/or close to 400nm where the LED has very little power. In absolute terms, as with gallery lighting, equiluminous exposure to LED light results in slower fading than a UV-filtered broadband source like xenon.
The advantages of high-powered LED over xenon are:
The only substantive advantages of filtered xenon over LED are that it:
The results of a survey of over 230 colourants tested using both sources show that for routine lightfastness screening - where colourant responses are rated against those of the ISO Blue Wool Fading Standards – the two illuminants deliver very similar results. In some cases there are differences, most likely where the valley between the excitation and fluorescence regions of the LED spectrum overlaps activity spectra of particular colourants and/or close to 400nm where the LED has very little power. In absolute terms, as with gallery lighting, equiluminous exposure to LED light results in slower fading than a UV-filtered broadband source like xenon.
The advantages of high-powered LED over xenon are:
- much lower cost,
- chip life orders of magnitude greater than xenon bulbs,
- no OHS issues in relation to ultraviolet radiation. This may be particularly important for teaching institutions. Besides xenon’s steep purchase cost, replacements for the 3000hr rated bulbs cost more than US$3000.
The only substantive advantages of filtered xenon over LED are that it:
- more closely replicates sunlight through UV/IR filtered window glass
- can be used for extended wavelength UV-Vis-NIR Fibre Optic Reflectance Spectroscopy (FORS) (e.g. Aceto et al. 2014);
- can be used for activation spectral studies of non-lightfast colourants reaching down into the UV with appropriate bandpass filters (e.g. Lerwill et al. 2015).
DESIGN
The instruments are both based on Whitmore's original fibre-optic design, of which the most important features are its robustness, modularity, and that 3D and large objects are not required to fit within the constraints of a fixed height measurement head with restricted orientation. The 2 metre fibres, adjustable boom-arm, and X-Y base allow the measurement head to be rapidly and accurately positioned at any angle within a 50cm range. This largely avoids moving, manipulating or supporting large and 3D objects at odd angles for testing. It is unnecessary to flatten pages and stress spines of books and manuscripts; costumes and other objects can usually be tested within their storage boxes avoiding time consuming unpacking, handling, and repacking; and objects including textiles and pictures, may be tested in situ on walls. It is possible to bridge large paintings and textiles with 38mm (1.5”) aluminium tube supported at both ends. The 16mm effective focal length allows testing of most glazed pictures without de-framing.
The manual focus is simple, reliable and rapid, and the OD4 (1/10000x) neutral density (ND) filter used to attenuate the brightness of the illuminated spot in order to choose and record the test location is solenoid driven. The shutter is opened and closed with a switch on the LED lamp or remotely using a wired mouse-like switch. Microscope photographs of the exact position of the test are obtained with a high-resolution USB pen microscope housed within the MFT head.
Unlike older Newport units, the LED and Ocean Insight lamps require no user alignment or other maintenance, greatly simplifying setup, use and training. The Thorlabs ½” lens assemblies are fully assembled, tested and optimized before delivery.
Because it is modular:
The instruments are both based on Whitmore's original fibre-optic design, of which the most important features are its robustness, modularity, and that 3D and large objects are not required to fit within the constraints of a fixed height measurement head with restricted orientation. The 2 metre fibres, adjustable boom-arm, and X-Y base allow the measurement head to be rapidly and accurately positioned at any angle within a 50cm range. This largely avoids moving, manipulating or supporting large and 3D objects at odd angles for testing. It is unnecessary to flatten pages and stress spines of books and manuscripts; costumes and other objects can usually be tested within their storage boxes avoiding time consuming unpacking, handling, and repacking; and objects including textiles and pictures, may be tested in situ on walls. It is possible to bridge large paintings and textiles with 38mm (1.5”) aluminium tube supported at both ends. The 16mm effective focal length allows testing of most glazed pictures without de-framing.
The manual focus is simple, reliable and rapid, and the OD4 (1/10000x) neutral density (ND) filter used to attenuate the brightness of the illuminated spot in order to choose and record the test location is solenoid driven. The shutter is opened and closed with a switch on the LED lamp or remotely using a wired mouse-like switch. Microscope photographs of the exact position of the test are obtained with a high-resolution USB pen microscope housed within the MFT head.
Unlike older Newport units, the LED and Ocean Insight lamps require no user alignment or other maintenance, greatly simplifying setup, use and training. The Thorlabs ½” lens assemblies are fully assembled, tested and optimized before delivery.
Because it is modular:
- if the lamps and spectrometers should fail they can be replaced without sending the instrument away for service.
- the high-resolution spectrometer can be detached and used for standard colour measurement, illuminant (including LED) characterisation, filter characterisation (for example UV/IR blocking window films and picture glazing), absolute irradiation measurement (W/cm^2/nm), and solution spectroscopy. Some of these uses require additional accessories such as calibrated light sources, integrating spheres, and cuvette holders. https://www.intechopen.com/books/11002.
UPGRADES for Older Whitmore Design MFTs
Older xenon lamp instruments, for example the original Newport benchtop and Apex MFTs, can be updated to LED whilst reusing many of the original components including the support and X-Y hardware, spectrometer, optic fibres, and most of the optics.
Older xenon lamp instruments, for example the original Newport benchtop and Apex MFTs, can be updated to LED whilst reusing many of the original components including the support and X-Y hardware, spectrometer, optic fibres, and most of the optics.
COMPONENTS
LED Lamp
- Osram Ostar Projection Compact, 400-700nm, cool white (~5000K)
- solenoid driven neutral density (ND) filter and remote switch
- adjustable thermostatically controlled constant-current power supply, 0.2A - 2.8A (max continuous = 3A). LED temperature control ± 0.2 degrees C (LED spectra are temperature sensitive).
- illuminated spot diameter: ~0.32mm for 200μm fibre, ~0.45μm for 300um fibre.
- power: 4.1mW max for 0.32mm spot (200μm fibre), 8.0mW max for 0.45mm spot (300μm fibre).
- illuminance:: ~14 megalux max, typical test illuminance = 5 - 8 megalux)
- optically quiet source, drift after warmup < 0.2 DE00/hr.
- SMA905 fibre optic connector
- two-year replacement warranty
Xenon Lamp
- Ocean Insight HPX-2000-HP-DUV 75W xenon lamp providing 185-2000nm broadband radiation for FORS applications and MFT. This is an optically very stable lamp.
- filtered 400-700nm for MFT with a removable visible bandpass filter housed within a Thorlabs FOFMS inline filter holder with a CFH2-V variable intensity attenuation shutter.
- well in excess of "normal" MFT intensities of about 6 mlux within the illuminated spot when new. The bulbs are nominally rated for 3000 hr but may last longer because of the excess brightness
- replacement bulb assemblies are factory pre-aligned.
- optically very quiet with excellent drift characteristics.
- completely enclosed optics to avoid UV safety issues.
- manufacturer’s warranty.
Spectrometer
- PerkinElmer (formerly Control Development) diode array spectrometer. It is the same spectrometer and Spec32 software familiar to existing users of Newport MFTs, and the only one for which my XL macro-based data acquisition, presentation and reporting system can be used.
- compatible with JP Brown’s update of the GCI SectralViewer software (below) which also allows use of Ocean Insight and Broadcom/RGB Photonics spectrometers.
- 200-1100nm with order sorting filter options for extended wavelength measurement. With a 100mm input slit, resolution is 0.2nm for 400-700nm and larger for greater dispersion.
- non-scanning (millisecond spectral acquisition), integration times 1.7ms to 16 seconds.
- high dynamic range for measuring small changes at high light levels.
- Manufacturer’s warranty.
Computer
- GMKtec NucBox G5 pocket sized minicomputer, 12gig RAM, 256 gig storage, N95 Intel Alder Lake N97 processor.
- WIN11 pro
- loaded and tested with all necessary software for MFT including MS Office 2021 (permanent license, not 365 subscription).
- client provides keyboard and monitor.
- OR laptop, fully set up, Win11, 15" screen, 128 or 256g storage, 16g RAM.
Software
- Perkin Elmer (formerly Control Development) Spec32 spectroscopy software including datalogging and live colour change (ΔE) tracking.
- Excel and PowerPoint VBA macros for Spec32 data acquisition, table and chart presentation and reporting templates.
- Getty Conservation Institute (GCI) Spectral Viewer MFT software initially developed for Spec32, updated and improved by JP Brown from the Field Museum. Currently SpectralViewer v.3.rc1a. It comes with a comprehensive manual and XL sheet containing a range of useful calculators.Can be obtained from Vincent Beltran at the GCI.
- MS Office 2021.
- GIMP and Paint.net imaging software, Better File Rename, other software as requested by client.
Last updated: July 2024