Opinion by

The defendants are extensively engaged in the manufacture of carpets. The value of their products in the market and the demand for them by purchasers depend largely upon the artistic character of the patterns or designs upon which they are made, and the harmony and general effect of the shades of color by which they are brought out. The designs are prepared by persons employed for that special purpose. When a new design has been made and adopted by the manufacturers, it is sent to the color room, which is in charge of a color mixer. The duty of the color mixer is to prepare the dyes or colors so as to reproduce in the carpet all the shades indicated by the design. He submits the results of his work to the designer. When approved, it becomes his duly to enter in a book kept for that purpose and called a “ Color Book,” the number of the carpet and the formula by which each shade of color used in its manufacture is produced. He is also required to keep a book in which a piece of yarn, colored according to the formula, for each shade in the carpet, is preserved, with the number of the carpet to which the shades belong. This is known as the “ Shade Book.” When the manufacture of this particular carpet is about to be begun, the color mixer prepares the colors for actual use. When mixed and ready for use, they are put into large pitchers and on each pitcher is put a label with the formula or recipe by which the color it contains was prepared, together with the number of the carpet upon which it is used; so that when a pitcher is emptied it can be refilled by any of the employees about the color room by following the recipe appearing *130on the label. The designer and the color mixer, like the printer and the weaver, are employed, and their wages adjusted with reference to their skill and experience in the department of work to which they are assigned. They are not independent contractors producing designs or shades of color by a secret process of their own which they sell as patterns or colors to the manufacturer for a fixed price, but they are employees bringing their skill and experience, in the use of the materials furnished by their employer, into his service for his benefit in the production of his goods. The designs and recipes so made for him are, as between his employees and himself, his for the purposes of Iris own' manufacturing business. Even if his employee had obtained letters patent for Iris formula protecting himself thereby against the public, still the employer’s right to continue its use would be protected by the United States Courts: Solomons v. United States, 187 U. S. Rep. 342. The same conclusion was reached by this court in Slemmer’s Appeal, 58 Pa. 155, where we said, “ If one employed by another, whilst receiving wages experiments at the expense of his employer, constructs an invention and permits his employer to use it without compensation paid or demanded, and then obtains a patent, a license to the employer to use the patent will be presumed.” But this case is much stronger than that of one who obtains a patent as in Slemmer’s case, for here the experiments resulting in the recipes were not only made at the expense of the employer, but for him, and with a view to the immediate use of their results in his business. It was the sole and only purpose for which the color mixer was employed and paid. In the manufacture of carpets, the spinning of the yarn is no more a part of the process than is the preparation of the colors to be made use of in working out the pattern. The fact is that the spinner and the weaver, the color mixer and the printer who uses the colors, are all alike in their relation to their common employer. The labors of all are necessary to the production of a carpet and the results of the labor of all belong to the employer who pays for the labor. The recipes prepared by the color mixer, for the use of his employers in the manufacture of their carpets, belonged to them so far at least as to give them the right to continue the use of the various colors and shades produced by them. The plaintiff had a right if he chose so to do, to preserve them for his own *131use in the future, but his right was not an exclusive one. It was his duty by virtue of his employment and by reason of the relation his work bore to his employer’s business to enter all these recipes in his employer’s color book; for none of the patterns of carpet manufactured during the twenty years of the plaintiff’s service could be reproduced without the use of the same recipes, for the preparation of the colors to be employed, that had been used when the pattern was first produced. This duty, to put it in the mildest form, the plaintiff had improperly neglected. His employers were left under the belief that their color books had been used and that the books he was attempting to carry away were in every sense of the word their own property. Had this been true, their conduct in requiring him to leave them in the mill would have given the plaintiff no cause of action. In respect to this subject the mistake under which they labored was due to the plaintiff’s failure in duty as an employee. He had pushed the blanks furnished to him to one side and had used only his own, and had left his employer in ignorance of his conduct. Now let it be conceded that the books he was attempting to carry away were his own; it is nevertheless true that they contained the only record of the recipes used in the mill for twenty years, and that these recipes were a part of the stock in trade of his employers. Not perhaps the particular copy of them which the plaintiff had entered in his own books, but the processes and combinations they represented belonged for the purposes of their business to them, and as between him and them they had a right to some record or register of recipes.

If the plaintiff had a light to recover in this action because of the ownership of the books in which the recipes had been entered and the manner of his detention, when he attempted to take them away, the jury should have been instructed that the value of the recipes was not to be considered in estimating the damages. As between these parties, as we have already said, the plaintiff had no exclusive right to thorn. It was his duty as a color mixer to enter each formula in his employer’s books. They had a clear legal right to the knowledge which such a record would afford them, and the copies they have made from his books should have been made for them by the plaintiff as the several colors were compounded during his long term of *132service. The plaintiff’s claim for damages must rest on the fact that he owned the books that were kept from him. In addition to this, anything in the manner of the detention that shows unnecessary violence or disregard for the sensibilities or the self-respect of the plaintiff may be considered. But the jury should be told in this connection that they should also consider the conduct of the plaintiff — his disregard of his duty and his instructions in making no entries in his employer’s color books — his failure to disclose this fact to them, and leaving them under the honest belief that he was removing from their mill their own color books. The portions of the charge embraced in the fifth, sixth and seventh assignments of error, if stated as abstract propositions would be unobjectionable, but as applicable to the facts of this case they were in the view we have taken of this case misleading. The plaintiff does not seem to have suffered any special inconvenience or injury because of the detention of his books and he has no right to complain that the defendants are now in possession of one list or register of their own recipes. They are entitled to such a register and it should have been made for them by the plaintiff. If he had discharged his whole duty as an employee, the misunderstanding which led to the detention of his books could not have occurred and this litigation would never have arisen. The first assigment must also be sustained. The letter written after the plaintiff’s color books had been returned to him demanding that the copy that had been made should be given up to him was inadmissible. It was an argumentative presentation of his view of his rights as an employee and of the grievance of which he complained. It was unanswered. It was the declaration of the plaintiff in his own behalf and was no more admissible because reduced to writing than it would have been if delivered orally. The point is substantially ruled in Fraley v. Bispham, 10 Pa. 320.

The judgment is reversed for the reasons now given and a venire facias de novo awarded.