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Trial Number 1

Trial Purpose:

To evaluate hard water stain removal

Date Run:


Experiment Procedure:

A good way to predict the effectiveness of an acid is by means of the so-called “marble block” test method. This test is a good way to predict an acid’s performance under practical conditions.
To test the descaling performance, a marble block is submerged in a test solution for several minutes. The weight is measured before and after.

Several marble chips of similar size and shape were weighed to determine the baseline weight of each piece. The selected chips were then immersed in the products at vendor recommended dilutions and allowed to soak for 18 hours. The marble chips were removed from the products and rinsed in a tap water spray at for 1 minute to remove loose material from the chips. Then the chips were dried for 15 minutes using a Master Appliance Heat gun at 500 F. When the chips cooled to room temperature, final weights were recorded to determine weight loss, if any. Observations were made after the initial immersion of the chips into solutions (5 minutes), at 60 minutes and then following the overnight immersion.

In addition to the 4 products from the soil removal test, 2 additional products were included for hard water stain removal.

Trial Results:

The current toilet bowl cleaner from TMI was by far the most effective hard water stain remover based on weight loss of the marble block and visual observations. The PC 120 was the second most successful product from the previous trial. The two additional products, DFC Restroom and CLR, also were effective at low concentrations. The table lists the amount of calcium removed from the marble and the observations on the process.

Product Initial wt Final wt Diffeerence %Wt loss of block Ave 
TMI Toilet Bowl - porcelain 16.9467 16.6224 0.3243 1.91 3.91
  7.1301 6.7089 0.4212 5.91  
Tough Job - porcelain 14.6607 14.6712 -0.0105 -0.07 -0.06
  9.8936 9.8993 -0.0057 -0.06  
7th Generation All Purpose - porcelain 20.2033 20.1934 0.0099 0.05 0.12
  7.1918 7.1781 0.0137 0.19  
PC120 - ceramic 13.4153 13.3580 0.0573 0.43 0.33
  8.4230 8.4028 0.0202 0.24  
DFC Restroom 19.8850 19.6572 0.2278 1.15 1.40
  4.8122 4.7330 0.0792 1.65  
DFC CLR 11.4138 11.3263 0.0875 0.77 1.19
  4.0115 3.9467 0.0648 1.62  
Visual Observations        
Product Initial 5 min 60 min 18 hr
TMI Toilet Bowl - porcelain Aggressive mild particles collecting on bottom particles collecting on bottom
Tough Job - porcelain little little/none white haze particles collecting on bottom
7th Generation All Purpose - porcelain none none none  
PC120 - ceramic none none little particles collecting on bottom
DFC Restroom slight slight none particles collecting on bottom
DFC CLR none none none particles collecting on bottom

Success Rating:

A follow up test, usually based on company input.


Additional marble block testing will be conducted to try and identify more effective alternatives to the current cleaning product.

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