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Question for Metallurgists Regarding Contraction and Expansion of Metal to Temperature

The Cliffs Notes question is: Would it be possible for a razor, when exposed to either hot or cold water, to change tolerances enough due to expansion or contraction of the metal to impact the shave?

For the specifics, please read below.

I've used the same razor and blade almost exclusively for the last 3 years with hot water and always got great shaves. This summer, I decided to try cold water shaves and got slightly better results. However, as we approach winter, the water coming out of my tap has gotten colder than it is during the summer and early fall.

Tonight was probably the coldest water I've shaved with and no matter how I adjusted the angle, the shave was rough and not nearly as smooth as usual. Halfway through the first pass I switched to rinsing the razor with hot water and immediately the shave returned to the usual smoothness that I get from this razor.

Everything I've done with my cold water summer shaves was the same as tonight except for the temperature of the water I rinsed the razor with. Tonight, I turned on the hot water handle a little bit while wetting my beard because I don't splashing my face with the extra cold water I have at the moment. So that part was essentially the same as my summer cold water shaves.

The only conclusion I can come to is that the colder water caused the razor metal to contract slightly and changed the way the blade contacts my face. But, at the same time, it seems like the difference between hot and cold water wouldn't be enough to make a difference due to metal contraction or expansion.

The razor in question is made out of titanium if that makes a difference. Interested to hear from any metal experts who can comment on how metals expand or contract at different temperatures.
 
The Cliffs Notes question is: Would it be possible for a razor, when exposed to either hot or cold water, to change tolerances enough due to expansion or contraction of the metal to impact the shave?

The short version is: the change in dimensions of a typical stainless steel razor blade would be too small to notice.

It's been awhile, but a rough value can be calculated using some estimated figures. A key factor is the Coefficient of Linear Thermal Expansion. For razor steel, I am estimating a value of 11 from a lookup table.

COLTE (material, razor steel) ≈ 11
Width of blade (mm) ≈ 22
Temperature difference (Centigrade) ≈ 15

Using an online calculator, we get this result:

1699846676306.png


The calculated change in width of 0.0036mm is so small it should not be noticeable.
 
Different metals have different expansion coefficients, so yes, it's possible that the blade shrank enough more than the razor head to give you inadequate blade exposure and hence pulling.

Never a problem for me because I don't like cold shaving.
 
Different metals have different expansion coefficients, so yes, it's possible that the blade shrank enough more than the razor head to give you inadequate blade exposure and hence pulling.

Never a problem for me because I don't like cold shaving.

The coefficient of thermal expansion for titanium is close to razor steel, so I don't see how you can say that. Depends on the alloy, but tables say 8-9 approximately. Compared to 11 estimated for razor steel.

When the total change for a blade is 0.0036mm and the total expansion for a piece of titanium of similar dimensions is 0.0028mm; that is less than 0.0006mm difference. I don't see how a person could feel 6/10000 mm in blade exposure.
 
The short version is: the change in dimensions of a typical stainless steel razor blade would be too small to notice.

It's been awhile, but a rough value can be calculated using some estimated figures. A key factor is the Coefficient of Linear Thermal Expansion. For razor steel, I am estimating a value of 11 from a lookup table.

COLTE (material, razor steel) ≈ 11
Width of blade (mm) ≈ 22
Temperature difference (Centigrade) ≈ 15

Using an online calculator, we get this result:

View attachment 1747574

The calculated change in width of 0.0036mm is so small it should not be noticeable.

Thanks for the technical response, I appreciate it. I'll be shaving tonight and I think I'll do half my face with cold water and the other half with hot. Hopefully I get good a good shave on both sides. Clearly the metal isn't changing dimensions enough to make a difference so I'm not sure what the issue was with the last shave.
 
Think about how flexible your skin is in comparison. You're over thinking this.

... Thom
I see no reason why this could not be a factor if we are talking temperature and potential expansion/contraction. I have never studied how the microscopic edge of a razor reacts when hot vs cold but would bet it would be different, even if just marginally. All factors play a role, no matter how minute and when you add a handful together they may not being as minute as we thought. Either way, enjoy the journey
 
I see no reason why this could not be a factor if we are talking temperature and potential expansion/contraction. I have never studied how the microscopic edge of a razor reacts when hot vs cold but would bet it would be different, even if just marginally. All factors play a role, no matter how minute and when you add a handful together they may not being as minute as we thought. Either way, enjoy the journey
Anything is possible, but I read your comment as relating to a razor's flexibility and not that of thin, fragile razor blade edges.

I get your point about stacking "errors" on top of each other, and it's a good one but I don't think it applies to your original question.

I'm open to being proven wrong ;-)

... Thom
 

luvmysuper

My elbows leak
Staff member
Is the temperature of the water you use on your face to wet it, and to make lather the same as when you were getting good shaves?
I have to think that the lather and whisker/face skin reaction to temperature changes is going to be significantly more than any possible change in expansion or contraction of the metal in the razor and/or blade.
 
Interesting discussion!

My own $0.02, as a non-metallurgist is that changes in your skin and/or lather are more likely explanations.
 
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