Study of Toner Penetration in Papers by Laser Induced Plasma Spectroscopy and Optical Profilometry

Round 1

Reviewer 1 Report

1. Color symbols should be used for free in Figures 4,6,7 for reader's clarity.

2. The authors should explain why the coating removal corresponds to 15-20 microns in Fig.3 , while Ti distribution has a maximum at 20-30 micron depth in Fig.6.

3. Caption to  Fig.4: (CMYK) should be deabbreviated, while the curves colored. Intensity in arb. units should be in Figs. 4-7.

4. Error bars should be added in the Figures 3-7 and through the text.

5. English should double-checked through the manuscript to avoid breaks and punctuation errors like "Three dimensional analysis of elemental distributions at 0,3 mm2 lateral resolution and from A method", "... each depth were made and the results averaged", etc.

Author Response

Comment answers

1. All figures have been reproduced for clarity of the readers
2. It is noted that the x-axis in Fig.3 and Fig. 6 refer to number of laser pulses used to remove the coatings, not  micrometer scales. For titanium removal in Fig.6  about 25 laser pulses, while for the coating removal in Fig 3. about 50 pulses are needed.  
3. CMYK abbreviation has been explained now also in the text
4. Error bars have been added in Fig. 3 where they are essential. In other figures we do not see the importance of error bars in particular in the spectra such convention is not used.
5. The entire text has bee rewritten 

Reviewer 2 Report

The manuscript describes a method to determine the average depths of toner penetration in laser-printed papers by analyzing elemental profiles of the relevant layers. The experimental results are interesting. In the experimental part, all materials and methods used are shown. Conclusions summarize the presented results. I have some questions and comments to improve this manuscript:

1.  The abstract section needs to rewrite in the correct sequence with more explanation.

2.     Can authors explain in more detail why it is important to study the average toner thickness and toner distributions in laser-printed coated papers?

3.     In the experimental part, the authors said a 3 mm aperture was used to obtain a flat-top beam profile, I think it would make more sense if given the spot size of the laser beam here.

4.     There are two images in Figure 5, and and I think it would be more helpful to label figures a and b and explain the content in detail respectively.

5.     All figures could be embellished. Correct typographical errors.

Author Response

Response to reviewer

1. Abstract has been rewritten
2. Entire text has been entirely rewritten and it should now be much more clear to people not in the paper printing field why base papers have to be coated to allow for high quality printing. Diffusion of the toners into the coating during the printing process finally determines the outcome of colors in printing. Hence there is a wide spectrum of toners and coatings, to know diffusion processes of the toners is of utmost importance for paper makers selling their brands to printing houses.
3. Spot size is given and this part of the experiment clarified
4. We made a totally new presentations of Fig. 5 with a) and b) markings
5. All figures have been made more reader friendly and a thorough effort put to remove typographical errors

Reviewer 3 Report

The authors report on a quantitative investigation of the toner penetration in paper by laser induced plasma spectroscopy and optical profilometry. The paper motivation is clear, the paper organization good and the writing style appropiate. I thus find the manuscript suitable for publication in Coatings. I have however few minor comments:

1) the experiments are performed on both base paper and coated paper. As not expert in the field I find not clear why the coating layer is added and why it is relevant.

2) the thickness of the coating layer is expressed in grams/m^2. I understand that it is a standard notation, but actually a thickness is a length and not a mass surface density.

3) In figure 4 and 5 the spectra are vertically and horizontally translated. While the vertical stacking is ok, the horizontal translation makes difficult to see that the peaks are at the same wavelength in all the measurements. I thus suggest to replot the spectra with only vertical stacking.

4)  In figure 6 and 7 the different lines are distinguishable only from the symbols, that are rather small. I suggest to add a well visible color variation between the different lines to make the Figures understanding easier.

5) It would be nice to see a comparison between the profilometry measurements used to determine the depth profile, eventually as inset in one Figure 3.

6) the ablation thickness/pulse is reported without any indication of the error bar.  As these values are used to move from profiles vs pulse number to depth profiles it would be important to quantify the uncertainty on this "calibration slopes" to estimate the uncertainty on the final depth.

Author Response

Response to the referee remarks

1. It is one of the major finding of the present paper that toner penetration is much inferior to base paper than into coated paper. Good penetration of the toner into the coating is an utmost necessity for production of a high quality print and determines also the quality printed color images. Paper industry has known this for years.
2. The referee is totally right. Now in the text I use the industry standard term coat weight throughout. Yet given the coat weight we can measure average coated thickness and also study its uneveness in papers.
3. Figure 3 has been redrawn according to reviewers suggestion. in Figs 5 we made new coloring but kept the format for clarity for clear observation of the accumulation of the Si and Ti elements on the topmost layer of the print.
4. Figures 6 and 7 have also been redrawn for better clarity
5. We understand that Fig. 3 combines the results from the ablation and the profilometric measurements. We added the error bars in the figure to describe uncertainties of our approach. Errors increase when moving to base paper regime.
6. Error bars added in figure 3 and it is seen that errors in the toner and coating regime are rather acceptable. 

Round 2

Reviewer 1 Report

Now the manuscrupt could be accepted