Photographic blue print materials were studied for the purpose of improvement of keeping property, of sensitivity, contrast and color density, from the standpoint of scientific photography. So, in our first work the method for estimation of photographic properties of the blue print materials was discussed, corresponding to the sensitometry of general photographic materials, and in these studies characteristic curves were taken as a basis of examination of these meterials.First of all, it was affirmed, that paper, as the supporter of sensitive reagents, must have moderate absorptive power for sensitive solution, so that the produced blue substance may be fixed on fibre. In a word, surface property of supporter is considerably important and is closely concerned in photographic properties. According to our results, e.g., precoating of dextrin or gum-arabic before preparation of blue print paper had least effect for betterment of materials, but precoating of 3% gelatin solution increased contrast and blue density. This gelatin effect may be due to fixing force of gelatin layer, and perhaps blue substance cannot flow out from this layer. On the contrary, only pale blue color will be produced after printing, when baryte paper are used, and this is evidently unsuitable for blue printing material.As a sensitive material for blue print, ferric ammonium oxalate was most fitted. and 15 or 20 times more sensitive than ferric ammonium citrate.Concerning the concentration of light sensitive solution of blue printing, it has become clear that diluted solution cannot make blue image deep, so that the concentration of sensitive solution must be great to a certain degree for practical use. Particulary, the effect of concentration of sensitive solutions on the quality of blue print materials becomes of consequence, when they contain a small quantity of potassium ferricyanide.Sensitivity of blue print materials decreases proportionally to the amount of ferricyanide. Consequently, sensitive solution for high speed material must include minimum quantity of ferricyanide, and at the same time, much ferric oxalate.As to the effect of addition of some sodium salts of organic acids, it was found out that sodium formate, sodium oxalate and sodium acetate were sensitizers for blue print materials, but addition of too much salts tended to low sensitivity and high contrast.