Safety razor finishes

With all the finishes in safety razors, I thought I would write a blog on the subject and talk a little about the different types, costs, benefits and limitations of different finishes. The subject of surface finishing is a very extensive topic. This article would be too long to talk too in depth about the subject. My intent is only to provide an overview of the processes so you can understand the topics and maybe ask the right questions. If you want to see more specifics, ping me, I can try to do a follow up on the subject in another blog...

I also want to talk a little about some other decorative finishes This subject is also very broad, for some this takes a lifetime to master, especially in high end watchmaking.

Typically, stainless steel and other metals use a number of different standards to define the finish. The most common standards and measurements are DIM, ASTM and Ra to name a few.
 
https://isofinishing.com/surface-roughness-in-manufacturing/

The term DIN is an acronym that stands for “Deutsches Institut für Normung” or “German institute for standardisation”. ASTM is the US version and stands for American Society for Testing Materials (ASTM). Ra is another acronym for measuring a surface finish, it stands for “Roughness Average.”

https://fractory.com/stainless-steel-finishes-din-astm/

 The long and short of these standards is that they attempt to quantify the difference between the “peaks” and “valleys” of a surface. They all have their drawbacks. Often times, manufacturers in and out of the shaving market create their own standards. Measuring a surface finish is very difficult and expensive which leads to a subjective perspective of how smooth or polished a surface is?

For the rest of this article I will reference the ASTM standard but I will also need to reference “Ra” on occasion as, for us, it is the clearest and most well defined for the average person, however I will try to reference other industry standards such as “True #8 finish” or “Super #8 finish”. Here is a chart that shows Ra(Microns) vs the ASTM standard for perspective:

* Hairline is another term for a rougher “Brushed” or “Satin” finish. Chart source:
https://www.imoa.info/stainless-solutions/archive/31/Stainless-steel-mechanically-applied-finishes.php

https://www.diamondbritemetals.com/post/explaining-astm-a480-a480m-18-general-requirements-for-flat-rolled-stainless

The ASTM standard uses the following grades:
No. 1 and 2 -  This finish refers to cold or hot rolled sheet and rod material i.e.  pickled (remove scales) hardened, cold or hot rolled. I should note here that the above material is the surface finish of the blanks we buy to machine our razors.

No 1 and 2 surface finish

No. 3 – A rough linear texture. Generally a 40-60 grit. There is no standard for a “Machine Finish,” but depending on the part or level of machining it could fall into grade 3. An Ra number might be a better gauge for a machine finish...A rough turned handle that was done in a lathe could be classified as having a “Machine Finish,” however some lathes can finish a surface very fine...closer to a No.4.

No. 4 – Also known as a “Hairline finish” a linear texture but even finer, typically created with a 60-180 grit. Also known as a “Satin”(120 grit) or a “Sanitary”(180 grit) finish.

No 4 finish

No. 6 -  Also a linear texture but even finer. A soft satin finish...grits 240-320 are used for this finish.



No. 7 – To achieve this surface finish, sanding to a 600 grit and then a 1 step buff is applied. At this level machine lines can be easily be seen…in other industries this finish is referred to as a “brush mirror” or “directional mirror” finish.

No. 8 – Highly reflective finish, grit lines removed however the faintest of machine lines can be seen. To achieve this step sanding continues well above 600 grit...we use +2500 grit paper prior to multiple buffing steps.

Mirror polished surface safety DE razor shaver

Super No. 8  - A true “Mirror Finish”! No machine lines, all machine lines removed. A hip joint implant or a military mirror/lens of some kind would be polished to this level. Diamond compound in excess of 200K grit is used to achieve this finish...

https://polishedmetals.com/metal-finishes/8-mirror/

The best finish is a Super No. 8 finish, however this surface finish, often found in the medical, military and arerospace industry, is especially expensive to produce. When we were just starting Carbon Shaving Co. I had the opportunity to meet and talk with a local company who polishes lenses for missiles in addition to medical devices...diamond paste, under a microscope is used to accomplish some of these finishes while holding the tolerances that are needed.

Now as a designer, we have to grapple with these finishes and decide what is the best finish for a razor application and how best to describe our finish. We refer to our finish as a “High Polish Finish.” We use grits and diamond paste higher then 100K grit on some surfaces, however we struggle to claim a “No.8” or a “Super No.8” finish on the entire Cx as some of our surfaces have machine lines which we still finish but keep in order to preserve the high tolerances of our “pinch design”, we also finish some surfaces with a knurling pattern. We choose a “High Polish” finish because we think it is the best quality for our razors. I’ll explain our rational:

1) A smooth surface provides the best corrosion resistance to the material. Crevices provide a starting point for corrosion to occur. A smooth surface is the most resistant to corrosion.

2) A smooth surface is easier to clean. The crevices in a less finished surface can collect bacteria and germs. This provides more space for them to live and grow.

3) A smooth surface provides the least drag on a surface (skin), and a polished surface provides the slickest surface.

https://pubmed.ncbi.nlm.nih.gov/11194050/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4969518/

Sometimes we employ a rough finish when we want the most adhesion. For example, when we are bonding stainless steel or titanium to carbon fiber, we create a rough surface. We also add knurling to enhance grip on the handle.

While the functional element would call for a complete polished surface, we also recognize the desire for the aesthetics to shine through. That leads us to the decorative finishes.

The material we use is of a premium nature, these materials are hard and require more time and effort to finish. Some of these metals include Titanium and the premium stainless steel grade of 316L, a far more superior quality stainless steel than the “free machining” grade of 303 stainless steel (I talked about grades and material in an earlier blog post https://carbonshavingco.com/blogs/resources-and-blog/machined-stainless-steel-safety-razor-grades-and-titanium ). By using premium metals we believe it gives us the opportunity to do more decorative finishes without compromising the needed corrosive resistance of our Cx razors. Some examples of these decorative finishes include:

1) Perlage finish – Perlage means “pearl” in French. In the high end watch industry, it is extensively used on the inside of watch cases. This finish is often used in the food and beer industry and can be done using an abrasive and a rotating applicator.



2) “2-Tone” -  We apply a fine etching to non critical dimensions and surfaces such as the underside of the base plate or the handles. This contrasting surface finish is often used in show car engines. We bring the surfaces to a polished state and then apply a fine etching to darken the metal. We have done limited editions using this finish, the contrast of a polished surface with the finely etched surface provides a striking contrast.

2-Tone stainless steel

3) “Satin” - Aesthetically a nice finish but not as corrosive resistant as a polished surface or even a No. 7 finish. The crevices provide a place for dirt and bacteria to collect. It can take less time to apply vs a polished surface but also requires skill and craftsmanship to execute well. The light scratches that ultimately appear on a razor are less visible on this surface.

While not a finish, stainless Damascus has a very unique surface with high and low valleys. Although the true secret of making Damascus steel was lost to time, today the efforts continue with more enhanced and exotic materials including stainless steel. From an Ra perspective this finish has a high Ra rating. What makes our Damascus unique, is we use a custom forged stainless Damascus made from both 304 and 316 grades stainless steel. We then carefully “etch” the material in acid, the acid attacks or erodes the 304 grade first creating 304 valleys and peaks of 316 revealing the forged Damascus pattern. We then finish the material carefully with numerous grades of grits followed by diamond pastes.

Damascus safety razor shaver stainless steel

Other finishes used in safety razors include:

1) “Stone washed” - This finish is created by tumbling a razor with pellets and a solution. Inexpensive, uniform and leaves a non reflective, rough surface.

2) “Bead Blasted” - Also known as sand blasted, this finish is inexpensive to apply vs any polished surface, it leaves a rough (compared to polished), uniform finish making the material more susceptible to corrosion, collection of bacteria and will provide more surface drag. Similar to our “2-Tone” finish...

3) “Passivate” - This is a widely used finishing process for all grades of stainless steel. A citric or other acid is used to remove free iron (iron will rust) from the surface. It also does a good job of cleaning the surface. This process will leave a very thin protective layer on the surface.

4) “Electropolish” - Electropolishing is a process that makes stainless 30x more corrosion resistant than passivation, it also removes surface imperfection more effectively...it is similar to passivating but more aggressive in removing free irons from the surface. It generally can’t be done in a small workshop as it is a very specialized, controlled process with highly toxic acids. If a metal is electropolished it is also “passivated” however if a metal is “passivated” it is not “electropolished”. We electropolish our Cx-316L razors prior to final finishing, it is one of the most effective ways to polish threads.

https://www.ableelectropolishing.com/resources/passivation-vs-electropolishing/

5) On a final note I can’t ignore chrome plating as a surface finish...very inexpensive to make and exceptionally smooth, close to a “Super No. 8” in terms of its smoothness, however it has 2 major drawbacks that prevent us from using it:

a) The razor will not last. Typically these razors can be mass produced and are cheap to cast and plate. They are made from a less corrosive resistant material than stainless and then covered in a strong but brittle layer of chrome. As a result, when a razor is inevitably dropped, a crack will start in the brittle material and corrosion will penetrate this crack in the surface. Another week point with chrome plating are threads which take a lot of wear..this wear causes cracks in the chrome, which will cause the threads to break off.

b) Chrome plating is a very toxic process to the individuals applying the plating and the environment. It is a highly regulated process in the USA and is toxic to the environment. Its one of the big reasons why it is typically done in 3rd world countries or China.

Most recently I was shown a chrome plated razor from a gentleman who had received it from his late father, unfortunately his piece had broken off at the threads...it was sad as he still kept it.

I plan to come up with more ideas for future blogs but if you have any added thoughts or questions, I would love to hear from you…


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