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topic 1122

Knoop hardness measurement of gold plating


We are trying to get more hardness deposit in our gold plated items so the gold would not get off. People at Enthone-Omi have told us about a measure of hardness called KNOOP.

We will like more information about it.


Jamyl D'Angelo
Lima Peru


Knoop hardness is a method of measuring a material's hardness by its resistance to indentation. The method uses a precision diamond indenter and loads of 1 to 1000 gf. The size of the impression is measured with a microscope.

We have used this method frequently for evaluation of plated metals. It can be done on polished cross sections if the plating is thick enough or directly on the plated surface if the finish is smooth enough.

larry hanke
Larry Hanke
Minneapolis, Minnesota


Hardness testing by indentation is the usual method, and may be called various names and have various units of measurement. You will not be able to measure gold electroplate hardness on the surface with a diamond indentor unless the gold is at least 20 microns thick, you will have to do it on a section, for which it will have to be at least 10 microns thick if you use a 1gm load. You will have no idea what I am talking about at this time, but investigate micro-hardnes testing as a subject and all will become clear. HOWEVER beware of assuming that wear is a function of hardness - it is not essentially so. A soft metal such as indium makes an excellent bearing surface for example. Generally wear is more a matter of design of two parts rubbing together. It is a complex subject, and you will need to do a lot of reading or employ a consultant. To simply chase a harder gold will probably not do you any good.

Peter Vivian


I am a post-graduate student investigating the variation in hardness of silicon in realtion to crystallographic direction as a means of modelling cutting/ dicing in IC fab. I am experiencing difficulty in obtaining a Knoop indenter and would be grateful for any information on where to acquire this. It would be used with a Tukon MO microhardness tester and if it could be purchased from a company near Ireland or one with a quick turnaround so much the better. I would also appreciate any comments or suggestions on the experimental procedure Lincoln O Riain, B.Sc. Department of Physics, University of Limerick, Republic of Ireland

Lincoln O Riain
University of Limerick, Ireland


I'm doing a research project where I'm planning to use knoop microhardness testing to assess damage done by some machining operations.

I have never used knoop before. My query is how the load time affecting the results of the tests. On the hardness machine that we have in the lab, there is a possibility of varying the load time from 5 sec to 30 s. So given that I need to apply a load of 100 kgf on a tool steel specimen, what would be the most approrpiate load time. Is there any guideline. I would appreciate any help for particular guidance on this issue. many thanks in advance.

Haree Ramasawmy
- Huddersfield, UK


I am in need of a knoop indentor . so kindly let me know the supplier of the same.

Rajendra M. Kelkar
Illinois Institute of technology - chicago.

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