Archive Science | archaeometallurgy
Jun 27 2013

Slag analysis – Schlackologie

Bastian Asmus


Slag samples of a medieval (12th century) copper smelting furnace.
Top left: #21, XPL. Under crossed polarisers the zinc sulphide can be seen as tiny dendrites within the glassy matrix. The other phases are willemite (wlm) and copper (Cu), which is usually asso ciated with the (Zn,Fe,Cu)S phase, an accompanying phase of copper matte at the Huneberg, from which it probably segregates upon solidification. Free iron oxides are seen as dark and much larger dendrites.
Top right: Another section of #21, under plain polarised light. It shows the abundant spinels, the iron oxides and copper inclusions. Most notably it shows the free baryte (brt) inclusion in the slag matrix.
Bottom left: #22, shows more free baryte (brt), together with a lead antimony matte. The long needles are a mixed iron and zinc oxides and are believed to be franklinite (frk?). #104, is rather more affected by corrosion than the other two samples. It shows mainly spinel (sp), free iron oxides and some willemite (wlm). Spinels are in the same order of magnitude than in the other samples.

The colloquial term Schlackologie is used by several German colleagues in the archaeometric sciences when it comes to the analysis and interpretation of mostly metallurgical slags. Literally it would translate to slagology. But why are slags investigated at all and what exactly is slag?

What are slags and what do they consist of?

Slags are by-products of metallurgical or pyro-technological processes and usually remain at the production site as waste product. For example metallurgical smelting slag is usually composed of five separate components:

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Jun 27 2013

High power LED microscope illumination

Bastian Asmus

[tab: Overview]
sam_3004Problem: Your microscope is fine working condition, the optics are flawless, but illumination is either dim, brightness is not adjustable or bulbs are hard to come by.

Soultion: Retrofit your microscope with a high Power LED microscope illumination and these issues are in the past. Suddenly light consuming microscopy methods such as for example polarising or dark-field microscopy cease to be a problem. The utilised LED CREE XM-L is easily powerful enough for these tasks. The LED is powered with a  maximum of  1600 mA. At core of the  illumination solution is a LED driver and dimmer that I have specifically designed for this task. You can even make videos without any problems.

Custom made LED adapters are used for fitting the LED to your microscope. Upon request we can also do the conversion.

[tab: Universal LED Controller]
Bild der Unterseite der LED Steuerung: Einstellung des Maximalstromes für die LED MikroskopbeleuchtungThe Universal LED Controller is able to drive and dim all prevalent LEDs. Brightness may be controlled continuously between 0 and 100 %. Especially the new and powerful LEDs require fine adjustment if they are used in the bright field. To this end the universal LED controller was fitted with switch reduce the maximum power to 160mA, and thus adjusting the brightness in the bright-field is possible with ease. Of course this range may also be set to a different level by the user.

Further the controller features a set of six pre programmed maximum ratings to be able to drive LEDs other than 10W LEDs such as the CREE XM-L, without danger of destroying them.

The controller uses a softstart, i.e. there are no flashes during turning on the LED.


[tab: technical data]

 LED Adapter

  • High Power LED illumination retrofit solution
  • custom turned and anodised aluminium heatsink
  • e.g. for Zeiss illuminator 467040 and Zeiss Illuminator 15
    • adapter for for Carl Zeiss Jena illuminators
    • adapter for Carl Zeiss Jena Jenaval, Jenamed,…
    • for PZO Biolar
    • Leitz Laborlux
    • Leitz Diavert Köhler illumination
    • JEOL Electron Microprobe
  •  UV /IR / colour LEDs may also be driven


  • Coarse adjustment 0-100 % light output (0-1600mA)
  • Fine adjustment is preset to 0 and 10% light output, may be set by the user
  • Maximum current may be set to: 1600, 1200, 900, 700, 350, 160 or 50mA
  • constant colour throughout the whole range
  • LED reaches a maximum of 65ºC under maximum current
  • Aluminium die cast enclosure in black, light grey ot hammerite (grey)
  • DC in  4,5-12V
  • reverse voltage protection
  • works well as battery driven device
  • designed and made in Germany

[tab: Gallery]

click on the images

[tab: Order info]

169 Euro
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please contact me
LED Universal Controller 1600 mA
LED Universal Controller 2300 mA
LED Adapter + LED Universal Controller 1600 mA
LED Adapter + LED Universal Controller 2300 mA
P&P (Germany)
P&P (Europe)
P&P (rest of the world)

Order at info [at] archaeometallurgie dot de or use the contact form in the lower right corner.