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Testing of porcelain enamel powderproperties

To maintain the reproducibility of your enameling process, it is important to monitorand control all major process parameters.

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

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

Adhesion Application rate luidity !article size distribution "urface resisti#ity

$nderneath you will find an outline of the a#ailable testing methods to measurethese powder parameters, as described in the international enamel literature and%orused by major powder suppliers.

http://www.ditmer.nl/EN/Enameling/Defects/Testing%20powder%20enamel.htm#adhesionhttp://www.ditmer.nl/EN/Enameling/Defects/Testing%20powder%20enamel.htm#ratehttp://www.ditmer.nl/EN/Enameling/Defects/Testing%20powder%20enamel.htm#Fluidhttp://www.ditmer.nl/EN/Enameling/Defects/Testing%20powder%20enamel.htm#sizehttp://www.ditmer.nl/Webshop/catalog/product_info.php/cPath/21_24_26/products_id/162http://www.ditmer.nl/EN/Enameling/Defects/Testing%20powder%20enamel.htm#ratehttp://www.ditmer.nl/EN/Enameling/Defects/Testing%20powder%20enamel.htm#Fluidhttp://www.ditmer.nl/EN/Enameling/Defects/Testing%20powder%20enamel.htm#sizehttp://www.ditmer.nl/Webshop/catalog/product_info.php/cPath/21_24_26/products_id/162http://www.ditmer.nl/EN/Enameling/Defects/Testing%20powder%20enamel.htm#adhesion

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Adhesion

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 standardsettings. After a certain time inter#al, the panel is subjected to an impact of a controlled force, which isreproducible.

Adhesion & ' powder weight after impact % powder weight before impact ( ) *++

According to the theory, there are two different methods :

"T!A - "hort Time !owder Adhesion T!A - ong Time !owder Adhesion

The only difference between the "T!A and T!A method is the duration of the time inter#al betweenpowder application and impact. '* minute #ersus */ minutes(

Test result 0onclusion according to 123

"T!A 4 5/ 3ery safe for the enamelling shop

5/ 4 "T!A 4 6/ With risk for the enameling shop

"T!A 7 6/ 8nsufficient for the enameling shop

9owe#er, please note that in order to get reproducible results, it is necessary to keep the followingtest parameters constant :

ilm thickness of applied powder

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un settings like tension, flow rate and atomizing air !ressure, temperature and humidity of compressed air Ambient conditions between application and impact orce of impact

"ources :

12; Test , page ?=.

!28-/+*, *==/, page ?.

Application Rate

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

8t may be measured by determining the gun output per unit of time and then using that #alue as adenominator for the amount of powder applied to a standard target at a gi#en time.

Application rate & ' grams on target % grams output from gun ( ) *++

"ources :

!28-/+*, *==/, page 5.

Laboratory equipment for wet enamel

slip preparation & testingThe following equipment may be used for testing #arious properties of wet enamelslip prior to application :

Equipment Purpose

@ayer knife %

enamel slip

gauge

0omparing quickly the consistency of wet enamel

slip without weighting. ore..

@ayer enamelfineness testsie#e

easuring the fineness of a wet enamelslip.ore..

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erro conescreen

easuring fineness of wet enamel slip

aboratoryfurnace

iring sample plates and%or products. ore ..

anual spray-booth

0apturing o#erspray enamel while manualspraying small batches and%or sample plates.

anual spray-gun

"praying small batches of enamel for producingsample plates

!ycnometer easuring specific gra#ity of enamel slip. ore ..