Laser-drilling apparatus includes a gas-discharge for laser emitting laser-radiation pulses, and two acousto-optic modulators (AOMs). The laser radiation pulses are characterized as having two temporal central portions between temporal leading and trailing edge portions. The AOMs are arranged to spatially separate the central temporal portions of the pulses from each other and from the leading and trailing edge portions of the pulses.

A hair-penetrating shield 220 comprises a tooth array having top 280 and bottom 290 surfaces. In some embodiments, for a majority of the teeth, a cross section of each tooth (for example, triangular in shape) has an asymmetric width profile such that the tooth cross section, on average, is narrower near the top of the tooth and wider near the bottom of the tooth. In some embodiments, a ratio between: i) a first average tooth width describing the average tooth width below the top-bottom midpoint; and ii) a second average tooth width describing the average tooth width above the top-bottom midpoint is at least 1.2, or at least 1.6. In some embodiments, a non-viscous hair-coloring agent is dispensed as a mist over the top of the surface of the shield so as to color roots of hair passing through the spaces between the teeth of the user's hair. In some embodiments, closely-spaced teeth of the hair penetrating shield protect the user's scalp from the non-viscous hair-coloring agent. Related methods and kits are disclosed herein.

Formulation delivery systems, formulation delivery devices, and formulation cartridges for the same are provided. Formulation delivery systems include a reusable handle, a formulation dispensing assembly, and a controller. The formulation dispensing assembly includes a reciprocating nozzle assembly and a pump. The reciprocating nozzle assembly is fluidically-coupleable to the formulation cartridge or the cleaning cartridge received within the reusable handle. Formulation delivery devices include a reusable handle configured to receive a formulation cartridge therein, and a formulation dispensing assembly disposed in the reusable handle. The formulation dispensing assembly includes fluid conduits, a pump fluidically connected to the fluid conduits, a reciprocating nozzle assembly, and a controller. Formulation cartridges include a reusable cartridge body, a valve frame, and a disposable refill packet reversibly-coupleable to the reusable cartridge body. The disposable refill packet includes a formulation packet and a body portion configured for insertion into the reusable cartridge body.

Provided are a hair dyeing method which causes a particular portion of hair to attain a different color than the overall color, and hair which is thus manufactured. The method includes steps of (a) applying a first dye to a plurality of hairs, (b) dividing the plurality of hairs, to which the first dye is applied, into specific units of hair, (c) marking a section in the specific unit of hair which will not be dyed, (d) tying the marked section in the specific unit of hair, (e) injecting water into a dyeing apparatus which is to be used in applying a second dye, (f) heating the water which is injected into the dyeing apparatus, (g) injecting a chemical and a dye into the water which is injected into the dyeing apparatus and heated, (h) introducing the specific unit of hair to be mixed with the water which is injected into the dyeing apparatus, (i) gradually raising a temperature of the water which is injected into the dyeing apparatus, (j) when the temperature of the water which is injected into the dyeing apparatus rises to a certain temperature, maintaining the temperature of the water for a certain duration of time, (k) verifying the color of the specific unit of hair, and repeating the step (g) when the color of the specific unit of hair is not a designated color, and (l) when the color of the specific unit of hair is the designated color, stopping the heating of the water which is injected into the dyeing apparatus, and draining the water from the dyeing apparatus.

Method for treating hair wherein a first hair treatment composition is applied to the hair, e.g. the hair roots and a second hair treatment composition is applied to the hair, e.g. the hair lengths and tips, wherein the pH of the second hair treatment composition is higher than the pH of the first hair treatment composition.