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Ditmer Trading & Consulting BV

Professional Services & Supplies

Testing methods & instruments
for vitreous (porcelain) powder enamels

To maintain the reproducibility of the coating quality at your enameling plant, it is important to monitor and control all major process parameters.

With regard to the electrostatic powder enamel application department, it is necessary to keep your ambient conditions, equipment settings and powder properties within strict tolerances.

Powder enamel properties

This web page focus on testing the properties of powder porcelain enamels, which may be characterized by the following parameters :

  • Adhesion
  • Application rate
  • Fluidity
  • Particle size distribution
  • Surface resistivity

  • Testing Equipment

    Powder enamel adhesion tester

    Equipment Specifications

    Test methods

    Adhesion checks are most probably the best indicator of the condition of the powder.

    The adhesion of a powder is usually tested by applying a normal coating on a panel at standard settings.

    After a certain time interval, the panel is subjected to an impact of a controlled force, which is reproducible.

    Adhesion = ( powder weight after impact / powder weight before impact ) x 100 %

    According to the theory, there are two different methods :

  • STPA - Short Time Powder Adhesion
  • LTPA - Long Time Powder Adhesion

  • The only difference between the STPA and LTPA method is the duration of the time interval between powder application and impact. (1 minute versus 15 minutes)

    Test result Conclusion according to DEV
    STPA > 75 % Very safe for the enamelling shop
    75 % > STPA > 65 % With risk for the enameling shop
    STPA < 65 % Insufficient for the enameling shop

    However, please note that in order to get reproducible results, it is necessary to keep the following test parameters constant :

  • Film thickness of applied powder
  • Gun settings like tension, flow rate and atomizing air
  • Pressure, temperature and humidity of compressed air
  • Ambient conditions between application and impact
  • Force of impact
  • Reference documents

  • DEZ Test Regulations, English Edition 1994, page 89.
  • PEI-501, 1995, page 8.

  • Testing Equipment

    Equipment Specifications

    Test Method

    The application rate of powder is generally used to determine the rate of material transfer.

    It may be measured by determining the gun output per unit of time and then using that value as a denominator for the amount of powder applied to a standard target at a given time.

    Application rate = ( grams on target / grams output from gun ) x 100 %

    Reference documents

  • PEI-501, 1995, page 7.

  • Testing Equipment

    Fluidimeter for porcelain enamel powder

    Equipment Specifications

    Test Method

    The fluidity of a powder (its ability to get whirled up in a gas stream) can be measured with a fluidimeter.

    The average outflow of powder in grams per sec are a good indication of a powder's fluidity.

    Fluidity Outflow in gr/sec
    Very good 4.0 - 3.5
    Good 3.5 - 3.0
    Fair 3.0 - 2.0
    Insufficient 2.0 - 0.0

    However, please note that in order to get reproducible results with this test, it is necessary to keep the following test parameters constant :

  • Quantity of powder used
  • Temperature and relative humidity of compressed air
  • Pressure of fluidization air
  • Stirring time before executing the test

  • The flowability of a powder may also be defined as the product of the following equation :

    Flowability R = M x h1 / h0

    where :

    M is the weight of fluidized powder expelled from the side port in 30 seconds.
    h1 is the height of the powder bed in the fluidized state.
    h0 is the height of the powder bed in repose.

    A flowability of 140 to 350 is generally recommended.

    Reference documents

  • DEZ Test Regulations, English Edition 1994, page 88.
  • Pemco Technical Information 10, American Edition 1987, page 6.

  • Testing Equipment

    Alpine airjet sieve for powder enamel analyses

    Equipment Specifications

    Test Method

    The gain size spectrum has a considerable influence on its electrostatic charging and aerodynamic characteristics.

    The share of coarse particles in a powder enamel can be determined by means of the Bayer test sieve with for example a screen aperture of 0.04 mm. (= 40 mu = 16900 mesh/cm2)

    The residue of powder (RP) in percentage by weight is a measure for the frequency of coarse particles.

    Since the powder particle size distribution is a "normal" distribution, the one point check is usually satisfactory for determining the acceptability of a powder.

    However, please note that the gain size distribution may be altered if the powder recovery at the application system is defective.

    A more advanced measurement method is the use of an Alpine air jet sieve for verifying powder enamel particle sizes.

    Reference documents

  • DEZ Test Regulations, English Edition 1994, page 87.
  • PEI-501, 1995, page 9.

  • Testing Equipment

    Equipment Specifications

    Test Method

    Resisitivity is determined by applying high voltage on a compressed powder enamel sample and measuring the resulting current.

    Reference documents

  • DEZ Quality Requirement, Edition 1, 1994, page 90

  • About Us

    Ditmer Trading & Consulting BV is a family owned company, which was founded by Ronald Ditmer in 2007.

    We are specialized in providing worldwide professional services & supplies to the porcelain (vitreous) enameling industry.

    Benefit from our experience

    Our Managing Director & Owner has been personally involved in 50+ industrial porcelain enameling projects since 1984, while working respectively for Ferro (Holland) BV, Smit Ovens BV, Smit Sinus Enameling BV, Nordson Corporation and/or Ditmer Trading & Consulting BV.

    Company details

    Ditmer Trading & Consulting BV
    Palissander 141
    3315MP Dordrecht
    The Netherlands

    Phone : +31-78-6169877
    e-mail :


    for further information and/or assistance


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