Hair bleaching process

Abstract

Hair bleaching process. The invention relates to a cosmetic hair bleaching process comprising at least the steps of: a) applying a bleaching composition comprising one or more persulfates to at least one strand of hair, b) exposing the hair impregnated with the bleaching composition to microwave radiation. Figure for the abstract: Fig 1.

Description

Title of the invention: Process for bleaching hair Technical field

[0001] The present invention relates to methods of bleaching hair. Prior art

[0002] Many hair bleaching techniques have already been proposed.

[0003] It is known in particular to use bleaching compositions containing persulfates, with or without hydrogen peroxide. The use of such compositions requires long exposure times and high concentrations of oxidizing agents, which is not always desirable from the point of view of safety or from the point of view of maintaining the integrity of the hair fibers.

[0004] In the field of surface maintenance, it is known to use microwave radiation to increase the action of detergents. In particular, applications WO 98 / 03621, WO 98 / 03622, WO 98 / 03623, WO 99 / 25802 and WO 99 / 37745 describe treatments of hard surfaces combining exposure to microwave radiation with detergents containing bleaching agents.

[0005] In the field of hair styling, applications DE 3148 538, US 2006 / 0108358, US 2010 / 0006116 or US 2007 / 056860 disclose the direct use of microwave radiation on the hair.

[0006] Documents US 2006 / 042649 and US 6,079,422 describe heatable curlers that can be placed in a microwave oven before use for rolling hair. In these documents, it is the aspect of heat generation by microwaves that is used but there is no direct contact of these microwaves with the hair.

[0007] Application WO 2013 / 183021 discloses a method for treating keratin fibers comprising the application of a shaping composition followed by the application of mechanical tension and then exposure to microwave radiation.

[0008] Applications WO 2011 / 141882 and FR 3 062 786 describe methods for treating hair with a step of mechanical tensioning and a step of exposure to microwave radiation.

[0009] Application WO 2019 / 122850 discloses a method for coloring hair using a coloring composition and simultaneous treatment with radio wave radiation of frequency between 1 MHz and 300 MHz.

[0010] Accordingly, in view of these documents, there is still a need to improve hair bleaching processes, by increasing their efficiency while while preserving the hair fiber as best as possible. Disclosure of the invention Bleaching process

[0011] The invention aims to meet this need and relates to a cosmetic process for bleaching hair comprising at least the steps consisting of:

[0012] a) applying to at least one lock of hair a bleaching composition comprising one or more persulfates,

[0013] b) exposing the hair impregnated with the bleaching composition to microwave radiation.

[0014] The method according to the invention makes it possible to obtain an improved bleaching treatment for the hair. The use of microwave radiation, while the bleaching composition is still present on the hair, provides targeted excitation of the molecules, making it possible to reduce the concentration of the bleaching composition and in particular the concentration of persulfate(s), providing the treatment with greater effectiveness. Thus, for an equivalent result, it is possible to reduce the concentration of persulfates and / or the exposure time.

[0015] The use of compositions having pH values ​​lower than those of known bleaching compositions is also possible.

[0016] The use of microwave radiation makes it possible to accelerate the bleaching reaction and therefore to reduce the necessary exposure time of the composition.

[0017] The durability and homogeneity of the results obtained from the process according to the invention are very good, and the damage suffered by the hair is reduced, the risks of irritation limited.

[0018] Different results are obtained depending on the duration of exposure to microwave radiation, depending in particular on the basic color of the lock of hair.

[0019] The duration of exposure to microwave radiation can vary from 1 second to 30 minutes, better still from 1 second to 10 minutes, even better still from 1 second to 5 minutes, most preferably from 1 second to 2 minutes.

[0020] The method according to the invention may further comprise one or more steps (c) of rinsing the hair, preferably a single rinsing step carried out after step (b) of exposure to microwave radiation.

[0021] The method according to the invention may further comprise a step (d) of shaping the hair, comprising in particular the application of mechanical tension to said lock of hair, in particular via a device for applying mechanical tension, having a receiving surface intended to receive the lock of hair, in particular a step of winding the lock of hair onto a curler.

[0022] The method according to the invention can thus contribute to a certain shaping of the hair, and also offers the possibility of carrying out the bleaching treatment and lasting shaping simultaneously.

[0023] In this variant, the shaping step (d) is preferably carried out before the step (b) of exposure to microwave radiation.

[0024] The method according to the invention may further comprise one or more pre-treatment steps carried out before steps (a) and (b), and / or before or after step (d), where appropriate.

[0025] The method according to the invention may further comprise one or more post-treatment steps carried out after step (b), and / or after step (c), where appropriate.

[0026] These additional pre-treatment or post-treatment steps may comprise the application of one or more additional compositions other than that present in step (a). The application of these additional compositions may or may not be immediately followed by microwave treatment.

[0027] In the case where a shaping step (d) is carried out, the pretreatment step may consist of the application of a composition comprising either one or more film-forming fixing polymers or one or more reducing agents for the disulfide bridges of the keratins. Composition

[0028] In a preferred embodiment of the invention, the bleaching composition is aqueous, preferably comprising at least 5% water by weight at room temperature (25°C) and atmospheric pressure (760 mm of mercury).

[0029] The bleaching composition may result from a mixture of several compositions, preferably being the mixture of an anhydrous composition al comprising one or more persulfates and an aqueous composition a2, the latter itself being able to be a mixture of at least two compositions.

[0030] The mixing of compositions a1 and a2 can be carried out at the time of use of the bleaching composition.

[0031] The persulfate(s) included in the bleaching composition are preferably chosen from ammonium persulfate or persulfates of alkali metals and / or alkaline earth metals, such as for example sodium or potassium persulfates.

[0032] The bleaching composition used in the process according to the invention may be as described in patent FR 2 975 291.

[0033] In the bleaching composition, the concentration of persulfates can vary from 1 to 60% by weight, better still from 5 to 50% by weight, even better still from 10 to 40% by weight relative to the total weight of the composition.

[0034] Where appropriate, the concentration of persulfates in the anhydrous composition al can vary from 2 to 80% by weight, better still from 10 to 70% by weight, even better still from 20 to 66% by weight. weight relative to the total weight of the anhydrous composition al.

[0035] The bleaching composition preferably has a pH greater than 7, preferably ranging from 7.1 to 13, better still from 7.5 to 12, even better still from 8 to 11.

[0036] The bleaching composition preferably comprises one or more alkaline agents. Said alkaline agent(s) may be contained in the anhydrous composition a1 comprising one or more persulfates and / or in the aqueous composition a2. Said alkaline agent(s) are preferably chosen from metasilicates, alkali metal and / or alkaline earth metal carbonates, ammonia, or alkanolamines.

[0037] Preferably, the bleaching composition also comprises an additional oxidant, in particular hydrogen peroxide. This hydrogen peroxide may come from an anhydrous hydrogen peroxide precursor such as urea peroxide then present in the anhydrous composition a1 which hydrolyzes in the presence of the aqueous composition a2. Even more preferably, the hydrogen peroxide may be in the form of an aqueous solution of hydrogen peroxide, called hydrogen peroxide, present in the aqueous composition a2.

[0038] In a preferred embodiment, the method according to the invention does not use any hair dye.

[0039] The cosmetic compositions used in the process according to the invention may also comprise at least one compound chosen from solvents, silicone or non-silicone fatty substances, anionic, cationic, non-ionic or amphoteric surfactants, silicone or non-silicone, polymers and in particular anionic, cationic, non-ionic or amphoteric treating, fixing or thickening polymers, disulfide bond breaking agents, anti-dandruff agents, or anti-hair loss agents. Microwave radiation

[0040] By “microwaves” is meant electromagnetic radiation with a frequency ranging from 500 MHz to 300 GHz.

[0041] Preferably, the frequency of the microwave radiation used in the method of the invention ranges from 500 MHz to 300 GHz, better still from 500 MHz to 10 GHz, even better still from 900 MHz to 5 GHz, most preferably from 2 GHz to 3 GHz.

[0042] The power of the microwaves used during step b) may be less than or equal to 500 W, preferably ranging from 30 to 300 W, better still from 100 to 250 W, even better still from 100 to 200 W or from 100 to 175 W.

[0043] Preferably, the surface power density on the hair, induced by the microwave radiation, can range from 0.1 W / cm2 to 100 W / cm2.

[0044] Exposure to microwave radiation can be carried out using a microwave emitting antenna, said antenna and at least part of the wick to be treated preferably being inserted into a microwave-tight enclosure.

[0045] Where appropriate, the enclosure, at least during step b), contains the hair to be treated and impregnated with the bleaching composition. By "containing the hair", it is meant containing the hair over all or part of its length and over a given width. The enclosure may cover the hair over a length, for example, greater than or equal to 5 cm. Thus, a length of at least 5 cm of hair may be treated at one time in the enclosure.

[0046] Said enclosure may be defined at least partially by a housing having a housing, configured to receive at least a portion of the hair to be treated and, where appropriate, a hair shaping tool, and by a cover pivoting relative to the housing between an open position giving access to the housing and a closed position, the microwave transmission antenna being arranged inside the housing.

[0047] In one variant, the enclosure is in the form of a headset.

[0048] The enclosure may be stationary relative to the hair treated during the emission of microwaves or movable relative to the hair, allowing a greater length of hair to be treated.

[0049] The enclosure may comprise at least one seal made of an electrically conductive material, for example elastically deformable, making it possible to shield the microwaves used during step b) while allowing the hair to exit the enclosure. The seal may comprise a foam charged with electrically conductive particles, a brush formed of electrically conductive bristles or a comb comprising metal teeth.

[0050] In the case where the enclosure is in the form of a helmet, the enclosure may comprise electromagnetic shielding through which the treated hair can pass. Such shielding makes it possible to treat the user's hair while protecting the user's scalp from the emitted microwaves. The electromagnetic shielding is formed, for example, by a grid or a metal mesh. Together

[0051] The invention also relates, according to another of its aspects, to a set for bleaching hair comprising at least one bleaching composition comprising one or more persulfates and a device adapted to exposing the hair to microwave radiation as defined above.

[0052] Said device may comprise a microwave transmission antenna, said antenna and at least part of the wick to be treated being in particular inserted into a microwave-tight enclosure, as described previously.

[0053] The microwaves may be generated inside said device adapted to expose the hair to microwave radiation or outside by a microwave generator, for example a solid state generator such as a magnetron. A generator An external microwave can power one or more devices according to the invention, in particular via flexible waveguides.

[0054] In one variant, the generator is located outside the enclosure.

[0055] In this case, the generator can be connected to a plurality of antennas each associated to a device suitable for exposing hair to microwave radiation.

[0056] Each antenna can be connected to a corresponding high frequency stage of the generator. Several antennas can be connected to the same high frequency stage of the generator.

[0057] In another variant, the generator is located inside the enclosure.

[0058] The emission of microwaves can be carried out by a non-rectilinear antenna, by example of helical type.

[0059] The antenna may be formed from a sufficiently rigid wire, for example with a diameter ranging from 1 to 3 mm, so as not to require any support or support rod for the turns. In a variant, the antenna comprises a flexible wire or a conductive track arranged on a support structure, in particular a helical one. This support structure may be made of any dielectric material, preferably PTFE or glass.

[0060] The antenna, when it is helical, preferably has a fixed helix pitch, for example ranging from 4 to 5 mm. The radius of the helix is ​​preferably constant, for example ranging from 4 to 10 mm. The diameter of the antenna is for example from 8 to 10 mm.

[0061] The axial extension of the antenna can vary from 50 to 80 mm, better from 65 to 75 mm.

[0062] The antenna may be arranged in a tube, in particular closed at one end. This tube may be made of PTFE or another dielectric material.

[0063] The antenna can also be embedded in a dielectric material, preferably flexible, in particular silicone.

[0064] Said device adapted to expose the hair to microwave radiation may comprise a tool for shaping the hair, in particular a tool for applying mechanical tension, in particular a curler. The term "curler" denotes a tool allowing the hair to be wound around the longitudinal axis of the device according to a defined diameter, thus creating a mechanical tension, depending on the diameter.

[0065] The shaping tool may be configured, if desired, to place the treated hair flat during microwave exposure.

[0066] The device may comprise a housing capable of receiving the shaping tool. Said housing may be coated with a conductive foam which is arranged so as to overflow into a hair exit slot. This makes it possible to obtain a good seal of the closure, thanks to the deformability of the foam at the slot.

[0067] Where appropriate, the shaping tool and the antenna form a unitary assembly which is introduced into the enclosure.

[0068] The shaping tool may be made of PTFE or other di- materials electrical, especially thermoplastics.

[0069] The device used to implement the method according to the invention may comprise an audible and / or luminous warning system, for example to warn the user of a microwave leak outside the enclosure and / or of an excessive temperature inside the enclosure.

[0070] The device advantageously comprises a safety system preventing the emission of microwaves until the enclosure is closed and / or in the event of abnormal operation, for example microwave leakage and / or excessive temperature.

[0071] The device may be configured to control the duration of microwave emission, so as not to reach a treatment duration likely to damage the hair.

[0072] The method according to the invention may comprise, before step b), a step of detecting the closure of the enclosure. For example, a contactor is actuated when the enclosure is closed.

[0073] The sending of microwaves may be conditioned on the detection of the closure of the enclosure. After sending the microwaves, the continuation of the emission of microwaves may be conditioned on the absence of detection of microwave leakage, in particular using a microwave-sensitive sensor placed outside the enclosure.

[0074] The method according to the invention may, in addition, comprise a step of detecting the placement of the hair intended to be treated, before step b). This detection step may be carried out for example by an optical sensor and / or a mechanical feeler. The detection may be carried out indirectly, if necessary, by detecting the placement of the shaping tool.

[0075] The method according to the invention may comprise, for example during step b), a step of measuring the temperature to which the treated hair is subjected. This step of measuring the temperature may be carried out by a thermometer without contact with the hair.

[0076] The device may comprise, within the same handpiece, the microwave generator as well as the shaping tool. By "handpiece" is meant a part manipulated by the user with one hand during hair treatment.

[0077] As routing means that can be used to route the microwaves from the generator to the enclosure, mention may be made of waveguides, for example a flexible coaxial cable with a length of less than 10 m, preferably less than 5 m, with an external diameter of less than 5 cm, preferably less than 2 cm.

[0078] The device may comprise a sensor sensitive to a characteristic of the hair, for example the color, the mechanical resistance, the surface condition, the humidity, and the device may control at least one parameter of the treatment as a function of the characteristic. characteristics thus detected, for example microwave energy, solvent temperature, treatment duration and / or mechanical stress exerted, if applicable.

[0079] The characteristics stated above for the method apply to the whole, and vice versa. Brief description of the drawings

[0080] The invention will be better understood upon reading the following description and examining the accompanying figures. These are presented for information purposes only and in no way limit the invention.

[0081] [Fig-1] [Fig.l] illustrates different steps of an example of a bleaching process hair according to the invention,

[0082] [Fig.2] [Fig.2] schematically and partially represents an example of a device suitable for implementing the method according to the invention,

[0083] [Fig.3] [Fig.3] represents the handpiece, open, of an example of a device suitable for implementing the method according to the invention,

[0084] [Fig.4] [Fig.4] represents the handpiece of [Fig.3], closed,

[0085] [Fig.5] [Fig.5] is a view similar to [Fig.2] of a variant of the device suitable for implementing the method according to the invention,

[0086] [Fig.6] [Fig.6] represents a shaping tool, once extracted from the handpiece of a variant of device adapted to implement the method according to the invention, and

[0087] [Fig.7] [Fig.7] is a cross-sectional and side view of a device suitable for implementing the method according to the invention and comprising the shaping tool of [Fig.6], when the enclosure is closed. Detailed description

[0088] Various steps of an exemplary hair bleaching method according to the invention are shown in [Fig.l] and will be described in detail in the following.

[0089] In this example, during a step 11, a bleaching composition comprising one or more persulfates is applied to at least one lock of hair.

[0090] In a step 12, the hair in contact with the bleaching composition is exposed to microwave radiation of a frequency greater than or equal to 500 MHz, preferably ranging from 900 MHz to 5 GHz. The duration of exposure to the microwave radiation preferably ranges from 1 second to 1 minute, better still from 2 seconds to 30 seconds. The surface power density on the hair, induced by the microwave radiation, can range from 0.1 W / cm2 to 100 W / cm2.

[0091] The method according to the invention further comprises, in the example described, one or more steps 13 of rinsing the hair, preferably a single step 13 of rinsing the hair carried out after step 12 of exposure to micro-radiation. waves.

[0092] The method according to the invention may further comprise a step 14 of shaping the hair, comprising in particular the application of mechanical tension to said at least one lock of hair via a device for applying mechanical tension, having a receiving surface intended to receive the lock of hair, in particular a step of winding the lock of hair onto a curler. Preferably and as in the example illustrated, this shaping step 14 is carried out before step 12 of exposure to microwave radiation.

[0093] The method according to the invention may further comprise one or more pretreatment steps 15 carried out before steps 11 and 12, comprising for example the application of one or more additional compositions other than that used during step 11.

[0094] One or more post-treatment steps 16 may be carried out after step 12 and / or after step 13, comprising for example the application of one or more additional compositions other than that used during step 11.

[0095] Preferably and as in the example described, the bleaching composition has a pH greater than 7 and is aqueous, comprising for example at least 5% water by weight at room temperature and atmospheric pressure. The bleaching composition may be a mixture of several compositions, being in the example considered the mixture of an anhydrous composition comprising one or more persulfates a1 and an aqueous composition a2, the mixing of the compositions being carried out at the time of use of the bleaching composition. The persulfate(s) included in the bleaching composition and their concentration are as described previously.

[0096] [Fig. 2] shows a device 100 suitable for implementing the method according to the invention, comprising a handpiece 3 connected to a base station 1, comprising a microwave generator, by a flexible waveguide 2, constituted by a shielded cable. The handpiece 3 is intended to be manipulated by the user in order to be placed close to the person's head to treat at least one lock of hair H, as illustrated. The handpiece 3 can be produced in various ways and defines a treatment enclosure 4 which is microwave-tight.

[0097] In the example shown in [Fig. 3], the handpiece 3 comprises a housing 10, defining a housing 6, on which a cover 11 is articulated using an axis 12. The handpiece is shown closed in [Fig. 4]. The flexible waveguide 2 has only been very partially shown in figures 3 and following.

[0098] The housing 10 carries an antenna 30 which is in the illustrated example of helical shape, with longitudinal axis 7.

[0099] The antenna 30 is composed in the example considered of a helical metal wire, arranged in a tube 32 of a dielectric material, for example silicone or PTFE.

[0100] The antenna 30 is supported at one axial end of the housing 10 by a flange 14 of the housing 10, of semi-circular outline.

[0101] The cover 11 has a similar flange 15 on the opposite side, to close the opening 5 of the housing 6, through which a shaping tool can be introduced into the handpiece 3.

[0102] The inner surface of the housing 6 is defined by an electrically conductive coating 7 which allows the microwaves to be reflected and makes the enclosure 4 microwave-proof. This coating 7 may be formed of a conductive foam, for example of a semi-cylindrical shape on the cover and the housing, in the form of a disc for the flange 15 and a ring for the flange 14.

[0103] The housing 10 and the cover 11 define an exit slot 19 for the hair, located at the bottom of a recess 18, on the side opposite the axis 12 of the hinge.

[0104] The coating 7 preferably projects into the slot 19, as seen in [Fig.7], so as to achieve a good seal of the closure despite the passage of hair. The edge of the coating can thus slightly exceed at 17 the edge of the body of the cover and that of the housing to close the slot 19.

[0105] The handpiece 3 comprises a member for locking the cover in the closed position, not shown, as well as an opening detector.

[0106] A temperature detector may be present within the enclosure 4, for example on an interior surface thereof, in order to measure the temperature of the treated lock of hair and a control system, for example a microprocessor, may make it possible to interrupt or modulate the emission of microwaves in the event of a detected temperature greater than a predefined threshold.

[0107] Several handpieces 3 can be connected to the same generator 1, as illustrated in [Fig.5]. Special variant

[0108] In a particular embodiment, the housing 10 defines a housing 6 for receiving a shaping tool constituted in the example considered by a curler 20, shown in [Fig.6]. The presence of the tube 32, shown in [Fig.3], in which the wire of the antenna 30 is arranged facilitates the insertion of the latter inside the curler 20.

[0109] This comprises several branches 21 which define a hair receiving surface H, of width L, measured along the longitudinal axis X of the curler 20.

[0110] In this example, the X axis is parallel to the axis of rotation of the cover 11 and coincides with the longitudinal axis 7 of the antenna 30.

[0111] In the example considered, the curler 20 comprises four branches 21, which are slightly curved towards the X axis and pass through a minimum distance to the X axis at midpoint. length approximately.

[0112] The branches 21 may have ribs 23 oriented perpendicular to the axis X to help keep the wick spread out on the branches 21, preferably occupying the entire width L in the most uniform way possible.

[0113] The branches 21 are connected at their ends to annular parts 25.

[0114] The curler 20 has teeth 26 at the ends of the branches 21, which laterally delimit the surface for receiving the hair.

[0115] The curler 20 can be made of any dielectric material, preferably PTFE.

[0116] The curler 20 preferably has a shape symmetrical in revolution with respect to to a median plane of symmetry perpendicular to the X axis.

[0117] The curler 20 comprises studs 27 with enlarged heads, connecting at their base to the corresponding annular parts 25, which bear on the covering 7, as illustrated in [Fig.7], to keep the curler centered in the housing 6.

[0118] The studs 27 are for example located between the teeth 26, as illustrated.

[0119] The width W of the outlet slot 19 for the hair can be slightly su greater than L, the length of the housing 6 being substantially equal to the length of the curler 20, such that the latter is immobilized both axially and radially in the housing 6, with a small clearance.

[0120] To use the handpiece 3, a lock of hair impregnated with bleaching composition is wound onto the curler 20, then the latter is placed inside the housing 10 by moving it laterally relative to the latter, introducing it through the opening 5. Then, the cover 11 is closed, and the hair comes out through the slot 19. Once the exposure to the microwaves has been carried out, the lock of hair is extracted by carrying out the operations in the reverse order.

[0121] Numerous modifications can be made to the methods and devices which have just been described, without departing from the scope of the present invention.

[0122] The invention is not limited to a particular type of shaping tool, or to a particular type of microwave transmitting antenna.

Claims

Claims

1. Cosmetic process for bleaching hair comprising at least the steps of: a) applying to at least one lock of hair a bleaching composition comprising one or more persulfates, b) exposing the hair impregnated with the bleaching composition to microwave radiation.

2. Method according to claim 1, wherein the frequency of the microwave radiation used in the method of the invention ranges from 500 MHz to 300 GHz, better still from 500 MHz to 10 GHz, even better still from 900 MHz to 5 GHz, most preferably from 2 GHz to 3 GHz.

3. A method according to claim 1 or 2, wherein the bleaching composition is aqueous, comprising in particular at least 5% water by weight at room temperature and atmospheric pressure.

4. Method according to any one of the preceding claims, in which the bleaching composition results from a mixture of several compositions, being in particular the mixture of an anhydrous composition comprising one or more persulfates (al) and an aqueous composition (a2), the mixing of the compositions being in particular carried out at the time of use of the bleaching composition.

5. Method according to any one of the preceding claims, in which the persulfate(s) included in the bleaching composition are chosen from ammonium persulfate or persulfates of alkali and / or alkaline earth metals, such as in particular sodium or potassium persulfates.

6. A method according to any one of the preceding claims, wherein, in the bleaching composition, the concentration of persulfates varies from 1 to 60% by weight, better still from 5 to 50% by weight, even better still from 10 to 40% by weight relative to the total weight of the composition.

7. Method according to any one of the preceding claims, in which the bleaching composition has a pH greater than 7, ranging in particular from 7.1 to 13, better still from 7.5 to 12, even better still from 8 to 11.

8. Method according to any one of the preceding claims, in which the bleaching composition comprises one or more alkaline agents, in particular chosen from metasilicates, carbonates of alkali and / or alkaline earth metals, ammonia, or alka- nolamines.

9. A method according to any preceding claim, wherein the bleaching composition comprises an additional oxidant, preferably hydrogen peroxide.

10. Method according to any one of the preceding claims, in which the exposure to microwave radiation is carried out using a microwave-emitting antenna, said antenna and at least part of the wick to be treated being in particular inserted into a microwave-tight enclosure.

11. A method according to any preceding claim, wherein the surface power density on the hair, induced by the microwave radiation, varies from 0.1 W / cm2 to 100 W / cm2.

12. Method according to any one of the preceding claims, in which the duration of exposure to microwave radiation varies from 1 second to 30 minutes, better still from 1 second to 10 minutes, even better still from 1 second to 5 minutes, most preferably from 1 second to 2 minutes.

13. Method according to any one of the preceding claims, further comprising a step (d) of shaping the hair, comprising in particular the application of mechanical tension to said at least one lock of hair, via in particular a device for applying mechanical tension, having a receiving surface intended to receive the lock of hair, in particular a step of winding the lock of hair onto a curler, the step (d) of shaping preferably being carried out before the step (b) of exposure to microwave radiation.

14. Assembly for bleaching hair comprising at least one bleaching composition comprising one or more persulfates and a device adapted to exposing the hair to microwave radiation with a frequency ranging from 500 MHz to 300 GHz, better still from 500 MHz to 10 GHz, even better still from 900 MHz to 5 GHz, most preferably from 2 GHz to 3 GHz.

15. Assembly according to the preceding claim, in which the device comprises an antenna (30) for transmitting microwaves, said antenna and at least part of the wick to be treated being in particular inserted into an enclosure (4) impervious to microwaves.

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