Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Testing of historical varnishes and lacquers

Testing of historical varnishes and lacquers

Testing of historical varnishes and lacquers

Dear forum members,

I am currently working on a 4-year PhD-project on the characterisation of historical varnishes and lacquers of the West (Northern Europe from the 17th century until the 19th century).
These coatings consisted mostly of 1 or more natural ingredients such as resins, gums and (essential) oils.

The aim is to reproduce a selection of varnish recipes and characterise changes of the mock-up samples before, during and after artificial ageing. We expect the layers to lose elasticity throughout the ageing process (due to increased polymerisation but also due to the loss of volatile plasticisers). Furthermore we expect that the layers become more and more hydrophillic.

Of course we will not test all physical and mechanical properties, since we do not have enough time to do so. Instead, we are mainly focused on the change of previous mentioned properties because we assume they have a direct impact on the conservation of these varnish/lacquer layers on furniture, etc.

On this matter, I have a few questions concerning some of our measurement techniques:

  • For the measurement of elasticity we use the TQC Pendulum Damping test (König, Persoz).
  • For measureing changes on a hydrophilic level we wil use the Theta Lite Optical Tensiometer.
  • Changes in gloss will be measured by the Elcometer 408 (Gloss- and DOI-meter)
  • Changes in scratch resistance will be measured by the Pencil Hardness test.
My questions are:
How does this test cope with aged surfaces that are having surface defects such as cracking (craquelé)? If this has an influence, how to cope with this so that these measurements are comparable with the measurements before ageing?
  1. What is the influence of brush-marks on the test results?
  2. What is the maximum surface irregularity in order to assure the measurement is valid? (I will produce mock-ups on a plywood substrate. Although it has not the tendency to warp it still might be the case that this will happen after the artificial ageing).
A rather similar question: since UV-radiation often leads towards a change of surface gloss (surface topography changes due to embrittle, sometimes comparable to blooming effect), how can the contact angle measurement in such case be comparable to the measurement before aging (when the coating has a very high gloss). I experienced that a powdery surface of course will influence the contact angle.

And a last question: after the sessile drop for the contact angle measurement is placed on the surface, how long do you wait before commencing your measurement (I was said that a delay of 15 seconds is often used, to avoid the measurement of irrelevant data).

Thank you in advance,

Vincent Cattersel
University of Antwerp
Conservation Sciences

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


White Paper - How ESI is Helping Move New Medical Device Product to Market Quicker & More Cost Effic
Early Supplier Involvement has long been a strategy employed by manufacturers to produce innovative products. Now, it almost seems like a necessity. Because decisions made in the design phase can positively affect product quality and costs, this can help add value to OEM bottom lines. This white paper will discuss many facets of ESI, including why it’s so valuable today, what challenges limit the benefits of ESI, how cost is impacted, and more. Download Now
White Paper - Moving to a Driverless Future
This white paper describes what we see as the best practices to support a sustainable engineering process for autonomous vehicle design. It exposes how to use simulation and testing in common frameworks to enable design exploration, verification and validation for the development of autonomous cars at a system, software and full-vehicle level to drive a mature product development process for automated driving. Download Now
Research Report - How Engineers are Using Remote Access
Remote access enables engineers to work from anywhere provided they have an internet connection. We surveyed our audience of engineers, designers and product managers to learn how they use remote access within their organizations. We wanted to know which industries have adopted remote access, which software they are using, and what features matter most. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close