Copper Sulfate – Saline Etch for Aluminum – Test 6: Bath Strength Test

Name: Tessa Chambers & Nick Osetek                                  Date: 4/5/2018

Room Temperature: 71*F                      Humidity, etc: Dry

Experiment Goal: To test the strength of our used bath and compare that to our control/untouched bath. We were using our control bath to compare bath color, to see if the plates etch differently, and compare pH readings. We tested 3-minute and 5-minute plates in each bath to see if the tone would come out differently due to the different strengths of the bath.

Plate Material: Aluminum (5052)

Plate Preparation (surface prep, ground application, image making process, etc): We cut 4- 3x3in plates. Then we buffed them with fine grit steel wool, degreased with Bon Ami, and backed with contact paper.

Evaluation of Plate Preparation: Small spots of grease showed up after we degreased our plates.

Etching Bath notes: We were closely evaluating the pH of each bath to compare strength while we were etching our plates. The pH of the bath before and after use was 3.8. We’re still not sure if pH or bath colour is a better way of determining bath strength. Our control bath was a clear bright blue due to non use, but a strange yellow settled to the bottom of the control bath that we didn’t recognize. Our original bath was much greener and milkier due to using it for a month with multiple  3×3 inch plates.

Time in Bath: Original bath- 3 min, 5 min     Control bath- 3 min, 5 min

After Bath Evaluation: Our original bath wasn’t nearly as hot or active as it had been the first few weeks of use. The control bath was much hotter since it was our first time using it. Copper residue built up in the control bath much quicker because of how fresh the bath was.

Removal of Grounds (chemicals used and evaluation of effectiveness): N/A

Inking Methods: Bone Black oil based etching Ink, 10% Burnt Plate Oil 00, wipe plate normally

Paper Type: Hahnemuhle Copperplate

Soaking Time: 5 minutes

Press, blanket set up and pressure: Praga press, 2 blankets, Right setting: 4/9  Left setting:5/9

Conclusion: The 3 and 5-minute plates etched in the control bath were much darker, compared to the 3 and 5-minute plates etched in our original bath. The plates from the original bath were much lighter compared to past 3 and 5 minute plates. Our pH readings for each bath are still fairly acidic which makes us question if pH is a valid factor in reading the baths strength.  We are noticing the weakening of the bath over time and use.

pH reader calibration.

pH reading of etching bath.

Repeated 3-minute etchings in search for consistency of bath strength. 4 prints on left were etched in a used bath while the dark print on the far right was etched in a brand new hot bath.

Repeated 5-minute etchings in search for consistency of bath strength. 4 prints on left were etched in a used bath while the dark print on the far right was etched in a brand new hot bath.

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