Your foil scans are "usable" Kudit, and we are grateful to have them. We have been "settling" for usable scans for years now. Basically we do not have a source for "perfect" scans any more, so we work with what we have. Just look at how beautiful
the old scans on Magic Librarities are.
I have given incorrect advice in the past, so take this with a grain of salt. Basically this is what I think I know based on my observations and research.
A scanner's sensor and light source determine quality. There are two main types of sensors: CIS (Contact Image Sensor) and CCD (Charged Coupled Diode). The major advantage of a CCD sensor is a wider range of focus. You can scan graded cards through thick plastic cases. Light sources include Cold Cathode Fluorescent Tube Lamps, White LED, and RGB LED. Fluorescent lamps have distributed light while LEDs have concentrated light. Fluorescent lamps take several seconds to warm up and are being replaced by instant-on, cheaper LED technology. It is difficult to find a CCD Fluorescent scanner with drivers for Windows 7, 8, or 10.
A light source is placed to the side of the image sensor. An angle is placed between the light source and the image sensor to ensures that direct light rays are reflected away to reduce glare on matte surfaces. In the case of concentrated LED light sources on highly reflective surfaces (Such as pre-release date stamps) all light is reflected away and the surface appears black. RGB LED light sources would be the worst for foil scanning since the individual colors can contribute to colored reflections. I theorize that Fluorescent light sources require different angles and proximity to the scanner glass. Since they are also a more diffused source of light, they produce high quality foil scans with low color casting.
People have tried placing a barrier between the cards and the scanner. Matte acetate, lamination film, anti-glare plexiglass, matte screen protectors, etc. These serve to diffuse the reflected light so that some of it actually reaches the light sensor. You get the right appearance, but the image is blurred and the quality of the scan is compromised.
I was not around the forums when our founding members were scanning "Perfect" foils. But it seems to me that they never had color casting issues and their date stamps were never black. Here is a short summary of scanners:
Skibulk
CanoScan 9000F Mark II - Verified UsableCCD LED
Usable for foils, moderately difficult to achieve white foil reflections
Woogerboy21
Epson Perfection 4490 Photo Scanner - Verified UsableCCD Fluorescent
Usable for foils, moderately difficult to achieve white foil reflections
PresetM
Cannon CanoScan 9950F - Probably Usable
CCD Fluorescent
Windows 7 Drivers Only
Unknown foil characteristics
Kudit
CanoScan LiDE 210 - Not Verified
Unknown foil characteristics
Tenminutegod? or Teppic?
CanoScan LiDE 220 - Not Verified
Unknown foil characteristics
These look promising, but are not confirmed good or bad:
Canon CanoScan 8600F
HP Scanjet G3110
Diffraction Grating - I wonder this might work since it's a clear material (vs a cloudy matte surface).