tarnish from apples

[caseman]

does anyone know why knives get tarnish fast when you peel an apple as apposed to an orange? is it the acid level?

[smiling-knife]

I'm no chemist but I think it may be the amount and/or maybe more so the type of acid. Oranges/lemons etc have citric acid where as apples have malic acid. I can't elaborate on the chemical difference. In Victorian Britain fruit knives were made with sterling silver blades because of silver's resistance to the acid. Back in those days the fruit was primarily local e.g., apples and pears. Silver seems quite resitant to the acid in these fruits compared to steel especially before stainless steel was invented. s-k

[caseman]

Thank you for your response ,so what you are saying, that is the reason why swiss Victorian army knives can tolerate apples and oranges because of the stainless steel!

[smiling-knife]

It is no coincidence that Sterling Silver blades (don't see many these days on modern knives) went out of fashion not long after stainless steel became commonly used (1920s) Cost was probably a factor as well. Swiss Victorian Army Knife? s-k

[sunburst]

As kids with new knives we always would stick our knives into potato's and usually after one night would have a fairly decent coloring..Of course mom would want to know why her potato's had knives in them


Sunburst

[wt3l]

OK Caseman,

I agree with Smiling Knife....malic acid is a colorless crystalline compound that occurs naturally in a lot of unripe fruit such as apples, cherries, and tomatoes, it is also used in the flavoring of wine. HAHAHAH I knew I liked it for some reason Also...Sunburst , I too have put many-a knife into a potato. heheheh my way of getting more potatoes at dinner later, ya'll....WT3L

[caseman]

Thank you for your response! But can you tell me again what does a potato do the blade of the knife? do you place it in a potato before or after it tarnishes?

As kids with new knives we always would stick our knives into potato's and usually after one night would have a fairly decent coloring..Of course mom would want to know why her potato's had knives in them


Sunburst

[El Lobo]

Placing a non-stainless (lower % of Chromium), carbon rich blade in anything acidic (fruit, potato, carbonated beverages, vinegar, etc.) will begin to speed up the discoloring process of the blade. This is black oxidization (often called patina). It is harmless, but will discolor some things you cut, (like apples), thus the silver fruit knives. Black oxide will inhibit the forming of red oxide (rust) to a great extent. Stainless steels will not react to these acids, though they may show some staining/discoloring...as they are not really completely stainless...more like STAINS-LESS.

Bill

[smiling-knife]

Hi all. El lobo just made a point I was going to raise. Stainless means that it is stain resistant not that it won't stain. I think CV blades have a higher percentage of carbon than the surgical steel. Thus, they are easier to sharpen. However, high carbon steel rusts very easily. By adding Vandium, it is brought up to a standard that might legitimately be called stainless. It is still prone to tarnish and rust. However, the surgical steel is more resistant to staining (e.g., alloyed with Tungsten I think) but does not have quite the same edge advantages. It is a compromise that seems to work best for many apllications. Before stainless steel was invented, steel was very high carbon content. Thus you don't and shouldn't expect to see many tarnish/rust free knives of more than 80 years of age. Even if well looked after the tarnish/rust is inevitable with the carbon steel. s-k

[Bear Claw Chris Lappe]

Cutting apples to eat is one ofthe first things I always use a Case CV blade for, 5-6 apples over the course of a week, and ta-da...nice patina for life!