X-ray Microscopic Examination of Soap Mixtures

Figure 1: Clipped volumetric rendering of a soap highlighting individual features within the sample

Babylonians were making soap around 2800 B.C., as revealed in an excavation of ancient Babylon. Mesopotamians, Egyptians,and the ancient Greeks and Romans also made soap, basically by mixing fat, oils and salts. In the early 1800s, discoveries about interactions among glycerin, fats, and acids marked the beginning of modern soap making.

Soaps are so good at cleaning because they are surfactants and emulsifiers. As surfactants (surface-acting agents), soaps wet surfaces easily because they reduce the surface tension of water. As emulsifiers, soaps suspend oil or dirt so that it can be removed. Manufacturers add various ingredients to make the soap smell, feel, look, and function better, including fragrances as well as abrasives, such as talc or pumice.

In addition to many cleaning applications, soaps and other surfactants are used in corrosion inhibition, ore flotation, the promotion of oil flow in porous rocks, the production of aerosols, and as germicides, fungicides, and insecticides.

X-Ray Microscopic Imaging of Soap Formulations

We imaged two different formulations of finished bar soap products using continuous rotation imaging with the SkyScan 1273 desktop micro-CT. Continuous rotation imaging allows for rapid aquistion times on samples where resolution is not as important and throughput is valued. An example would be the inspection of finished goods, such as the bars of soap discussed within this article.

While both soaps are likely similar in composition, formulation A contains both oatmeal and sand additives while formulation B contains coffee grounds as an additive to the base soap formulation. Micro-CT imaging can pull out subtle differences in X-ray interactions among the different components allowing us to visualize the location and distribution of the additives within the finished soap bar product.


Figure 2: Planar 2D views of the two soap formulations examined

As shown in Figure 2, the SkyScan 1273 micro-CT quickly produces a detailed three-dimensional dataset showing the presence of pores and additives within each soap bar .

Figure 3: High-resolution 2D slice through a portion of soap formulation A

While the bulk soap phase is shown in gray and the pores in black, the higher density sand components are highlighted in purple while the medium density oat husks are shown in green in this color enhanced slice through formulation A (Figure 3). The determination of each component within the mixture is achieved through careful image segmentation to isolate and extract information only about the specific components of interest.


Figure 4: Clipped volumetric 3D rendering of soap formulation B highlighting the coffee ground additive

Using CTVox, we interactively explore the dataset in 3D including adding layered datasets, textures, colors, and shadows to isolate and highlight features of interest within the sample (Figure 4). For formulation B we were able to locate and display the size and location of coffee grounds within the larger soap bar.

Figure 5: Volumetric 3D rendering of pores within soap formulation A (left) and formulation B (right)

Through segmentation of the dataset in CTAn, we isolated and quantified the porosity for both soap formulations before visually demonstrating the differences using CTVox (Figure 5). We calculated a total porosity of 0.5% for formulation A while formulation B was found to be around 1.75%. In examining the images of both samples highlighting the pores, the additional pores present in formulation B are evident visually matching the quantitative data.


The SkyScan 1273 is one of the most versatile instruments in the SkyScan portfolio with the highest energy X-ray source and continuous imaging mode as key features to differentiate it from the other products available. Both features were utilized for this project using the powerful X-ray source and the continuous imaging mode to acquire full datasets for both samples in about seven minutes apiece.

We hope you found this Image of the Month informative and encourage you to subscribe to our newsletter and social media channels in preparation for the continuation of our Image of the Month series next month.

Scan Specifications

Sample Soap Bar
Voltage (kV) 120
Current (µA) 300
Filter 0.5 mm Copper
Pixel Size (µm) 70
Rotation Step Continuous
Exposure Time (ms) 100
Rotation Extent (deg.) 360
Scan Time (HH:MM:SS) 00:07:04


These scans were completed on our SkyScan 1273 micro-CT system using the continuous imaging acquisition mode at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon 2.0 while visualization and volumetric inspection of the 2D and 3D results were completed using DataViewer and CTVox. Individual components were extracted and analyzed using Bruker CTAn.

Would you like your work to be featured in our monthly newsletter? If so, please contact us by calling Seth Hogg at 610-366-7103 or e-mailing seth.hogg@microphotonics.com.


Related Products

Related Articles

US Partner Form

    Coming Soon:

    Customer access to tips and instructional videos, method notes, tutorials, application notes, and other content to support your research.


    Service Engineer opening for Micro-CT Systems

    We are looking for a service engineer to join our team of experts in helping advance research by providing technical support and maintenance for micro-CT systems across the United States.

    Please submit resumes to: info@microphotonics.com

    Micro Photonics Inc.
    1550 Pond Road, STE 110
    Allentown, PA 18104



    WVC Annual Conference

    Las Vegas, NV
    February 19-21
    Booth 1484

    Privacy Policy

    What information do we collect? We collect information from you when you register on our site, place an order, subscribe to our newsletter or fill out a form. When ordering or registering on our site, as appropriate, you may be asked to enter your: name, e-mail address, mailing address, phone number or credit card information. You may, however, visit our site anonymously.
    What do we use your information for? Any of the information we collect from you may be used in one of the following ways:

    ; To personalize your experience (your information helps us to better respond to your individual needs).

    ; To improve customer service (your information helps us to more effectively respond to your customer service requests and support needs).

    ; To process transactions. Your information, whether public or private, will not be sold, exchanged, transferred, or given to any other company for any reason whatsoever, without your consent, other than for the express purpose of delivering the purchased product or service requested.

    ; To send periodic emails .The email address you provide for order processing, will only be used to send you information and updates pertaining to your order.Note: If at any time you would like to unsubscribe from receiving future emails, we include detailed unsubscribe instructions at the bottom of each email.

    Terms and Conditions

    Terms of Service for www.microphotonics.com

    Introduction. Welcome to www.microphotonics.com. This website is owned and operated by Micro Photonics Inc. By visiting our website and accessing the information, resources, services, products, and tools we provide, you understand and agree to accept and adhere to the following terms and conditions as stated in this policy (hereafter referred to as ‘User Agreement’), along with the terms and conditions as stated in our Privacy Policy (please refer to the Privacy Policy section below for more information).

    This agreement is in effect as of October 25, 2018.

    We reserve the right to change this User Agreement from time to time without notice. You acknowledge and agree that it is your responsibility to review this User Agreement periodically to familiarize yourself with any modifications. Your continued use of this site after such modifications will constitute acknowledgment and agreement of the modified terms and conditions.

    Responsible Use and Conduct. By visiting our website and accessing the information, resources, services, products, and tools we provide for you, either directly or indirectly (hereafter referred to as ‘Resources’), you agree to use these Resources only for the purposes intended as permitted by (a) the terms of this User Agreement, (b) the terms of any applicable confidentiality, non-disclosure, or other agreement between you and a third party, and (c) applicable laws, regulations and generally accepted online practices or guidelines.

    Call Now Button