Proper care and storage of gut strings is important to maintain their quality and longevity. Following these practices will ensure your strings produce the best sound and last longer.

Cleaning Gut Strings
The simplest, most effective method for cleaning gut strings is to wipe off the strings with a soft, dry cotton or microfiber cloth after each playing to remove rosin, dirt, and sweat. For the little hairs or whiskers that develop on a gut string, we recommend using a nail clippers to carefully cut those stray gut hairs. 

Storage
Strings should be kept out of direct sunlight and heat, and stored, ideally, in an environment with 40-50% RH (relative humidity).

Our recommendation for string storage is fairly simple, keeping in mind that humidity and temperature — especially big humidity swings — have the most detrimental effect on gut strings:

Strings On the Instrument
If the instrument is in use and played regularly, keep strings at tension; if it is being stored for a period of time, the strings can be detuned a tone or so. When not being played, we recommend an instrument be stored in its case with the lid closed, versus sitting on a music stand or left out in the open.

Strings Off the Instrument
Store gut strings in a cool, dry place, preferably in a sealed container.

Sanding Strings
We do not recommend using sand paper on a gut string. Sanding a varnished string will remove some or all of the varnish, and sanding a plain gut string can effect its structural integrity. A nail clippers is the safest way to carefully cut stray gut hairs.

String Oil
This is a frequently asked question, but we remain fairly neutral on the subject. Some people insist on using oil to wipe down strings, but we have not found it to be useful. If you insist on the need to use oil on your gut strings, almond oil is the least detrimental as it leaves behind little residue and will dry completely — versus something like olive oil which does not dry completely and can lead to strings becoming gummy.

Gamut Music does not recommend soaking strings in oil or any other solution as it may cause the material to expand internally and/or break down the bonds within the string.

Cleaning Solvents
It is NOT recommended to use alcohol or other liquid solvents on gut strings, as it will cause the material to physically break down reducing the lifespan of the string (and even damage the lacquer of an instrument).

How Do I Remove a Buildup of Rosin On My Strings?
The above being said, the best way to remove rosin buildup on strings is with denatured alcohol. This will remove the rosin and leave no residue on the string. Remember to use an almost-dry cloth to avoid dripping on the instrument or soaking the string. Removing a little at a time is the best way to go.

What Are Those Little Black Squares That Came With My String??
Those little black squares are anti-tarnish strips put in the envelopes of strings wound in sterling silver to avoid tarnish. Sterling tarnishes, turning black-ish in color, and cosmetically looks bad. The anti-tarnish strips react to hydrogen sulfide and other tarnish-causing gases to neutralize them. If the silver string tarnishes it is still perfectly fine, but these little squares help prevent tarnish.

Further Reading: Things to Avoid When Caring for Gut Strings
Gut strings are known for their warm and rich tone, but they require special care compared to modern synthetic or steel strings. Using improper methods to care for gut strings can lead to premature wear, tuning instability, and a compromised sound. Here's what you should avoid when caring for gut strings:

Exposing to Excessive Humidity: Gut strings are sensitive to changes in humidity. Exposing them to high humidity levels can cause them to swell and become unstable, leading to tuning issues and potential breakage.

Not Cleaning Regularly: Neglecting to clean your gut strings can result in rosin buildup, which affects their playability and tone. Wipe the strings after each playing session to remove excess rosin and sweat.

Over-Tightening: Gut strings require careful tuning. Over-tightening them can lead to increased tension, which can cause them to snap or become prone to buzzing against the fingerboard. Fine tuners and string adjusters are not intended for gut strings and those devices should be removed before installing gut strings on an instrument.

Using Harsh Cleaning Agents: Avoid using chemicals or cleaning agents on gut strings, as they can damage the natural materials. Stick to using a soft, dry cloth to wipe them down.

Not Winding Properly on Pegs: Properly winding gut strings on the pegs is crucial to prevent slipping and tuning instability. Make sure the strings are wound neatly and evenly, without overlapping or crossing over each other.

Subjecting to Drastic Temperature Changes: Rapid temperature changes can cause gut strings to expand or contract, leading to tuning instability or breakage. Avoid exposing your instrument to extreme temperature fluctuations.

Using Excessive Rosin: Applying too much rosin to gut strings can lead to sticky buildup and hinder their responsiveness. Use rosin sparingly and wipe off excess after playing.