Document JJVNVooJk1R1boYVEzXa9OJM6

V-l September 24, 1928. MEMORANDUM FOR FILES: The attached letter of September 19, 1928 from the Board of Eduoatlon, City of New York, should be jointly answered by Divisions V and IX. A great part of this letter is devoted to specifications for plaster. It is, therefore, suggested that Division IX answer the letter inserting the following: In regard to the painting of plaster, we quote the follow ing from page 44 of Technologic Paper 274: "Too muoh emphasis can not be laid on the thorough drying of all plaster, conorete, cement, eto., before painting. It must be remembered that such structures when new oontain much water, and unless sufficient time, under proper conditions of temperature and humidity, is allowed for thorough drying the water remaining in the < wall will eventually seriously injure any paint coating. It should be pointed out that a wall may appear to be dry on the surface but be still damp in the interior. Even when properly dried, new structures of this kind may contain free lime; hence, it is advisable when the structure is less than a year old, even if it is known to be dry, to apply before painting, an aqueous solution of zino sulphate (3 to 4 pounds crystallized zinc sulphate to 1 gallon of water). Allow this to thoroughly dry be fore applying paint." It is noted that the plastered surfaces are painted two or three months after the plaster is applied. Apparently the plaster is frequently applied directly to the tile or briok wall. We very much doubt the advisability of attempting to paint plaster that is applied directly on briok wall. The plaster should have air spaoe back of it so as to assure drying. In regard to the painting procedure, it is noted that you propose to use lead and oil paint for the second and third coats. There is nothing better that can be used for these coats. The specification for the first or primer coat is indefinite. There is no reason why if lead and oil paint is used for the second and third coats, that it should not also be used for the priming ooat. The correspondent is referred to Technologio Paper 274, page 36, for formula for priming coat for plaster using white lead. We are enclosing a copy of our Letter Circular 59, whioh lists the Bureau's publications on paint and varnish and gives information as to how they may be obtained. Enclosures Letter. LC 59 Percy n. nar&er Walter C. Martin, 'aomxygasr- a r c h it ec t MPCRlKtDOCNT OF SCHOOL. BUIUMNft* BOARD OF EDUCATION ^THE CITY OF NEW YORK, N, V* BUREAU OF CONSTRUCTION AND MAINTENANCE PLATBIWH AVENUE EXT, AND CONCORD STREET, BROOKLYN TtUMatE Cu mb e r l an d 10VP RkmiMce Ho. met.ff tumxcTt * t e n . KMB formulae Brooklyn, W.Y., September spzojt //re P ?$0a*thre/^Pire.oitoir rofetrhoe# Bureau of standards ^ ix >0 Dear sirt The Buredfc of Construction and Kaiutenanoe, W-uBfttlon, City of WsW'lfork, are very muck interested in Of Minting on plastered wails and ceilings. We have a ox this work to do in connection witn new school building' in Wsw fork City. Our expe ;5ri.ence in the past of painting is^iin^ has not be$n entirely eatisffcetory* 0< M|fP(iik ha* 1>een OO^etSd these walls and oil.- noyt space of time. fretuahtly before f&Sc re|tp,for Oocupaacpy iMiae 4 discolorations appear oh-tJSs: surface!* * ;' Cor'^ ep^iu^oations for painting; first re oontraetor to apply af l first coat. a priming coat of ah * brand* fhe brands of primer approved by this Department ar m|ai?nuffaaectttuirroedJby rresp^uttjai^e^^oiwirn^^ daped^iy for use as $. ooat caplastered surf* ooat we spesi^f second and third oodt OC ii On now ...,,....painting o usually started twd-'toiifcfee: months aitep ...... applied* While sorfaoeii|^dF^. is applied* there is'^ pOasiMlity tbAts#e^#lAiie; son* moisture or that theoihder concrete SiXiig plaster is applied, are not thoxoughlydHed eufcv contend with humidity in the air and conseauenteo moisture on wall surface! which is bound to see# construction. ^ What we now contemplate just what Ingredients can boused for the priming ooat or first'dlmt, aleo f ooat. Would It bs possible for you*, giving the ingredients whloh you would used en each of the three coats to be ceilings uhder conditions as given N 3607.01 joireotor Of Bureau of Standards -2- September 19, 1928 If, in your opinion, an exoess of any particular ingredient, which, you might incorporate in these formulae, would he a detriment to the paint, will you please so state. For your information in furnishing this Bureau with these formulae, the following quotations are given from our specification In connection with plaster work and painting: "PLASTER FINISHES: She contractor has the option of using a machine made lime mortar mixed at the building or an approved gypsum plaster for all surfaoes required to be plastered, excepting such surfaoes as ars specifically specified to have other finishes. The walla and ceiling of auditorium shall be plastered with lime plaster. Lime Plaster: The mortar shall be a mixture of lime putty, sand and hair or fibre binder. Lime putty shall be made from properly slacked quicklime which has been run through a 10 mesh sieve and allowed to cool for at leaat 10 days before sand and binder are incorporated; or from hydrated lime wet into paste and allowed to stand for 24 hours before sand and binder are incorporated. The mortar shall be machine mixed in the follow ing proportions*: For scratch coat mortar, 10 ctuft* of llm fputty, barrels of sand and binder In the proportions of lbs of hair or & lbs. of fltfe to 3 ou.ft. of lime putty; for the brown ooat, 10 ou. ft. of lime putty, $ barrels of Hand with binder in the proportion of 1 Id * of hair or fibre to 3 cu. ft* of lime putty* Scratch and brown coat mortars shall be gaged with Portland cement in the proportion of 10$ by volume of cement for scratch coat and 6$ by volume for brown coat* The binder shall be either water-soaked, well beaten, clean, long cattle hair or approved vegetable fibfe out in 2-inoh or 3-lnoh lengths* Gypsum plaster. -- Gypsum plaster shall be applied in acoordenoe with the manufacturer*a directions, which directions are hereby made part of this specification* White Finishing Coate --> Ail plastered surfaces, unless other wise specified, shall be finished with s white finishing coat troweled to a hard, smooth, polished sudhos* The mortar for the white finishing coat shall be a mixture of lime putty, white sand and Plaster of Paris. The lime putty shall be made from properly slaked quicklime whloh has been run through a 10 mesh sieve &M allowed to cool at least 10 days before Plaster of Paris is incorporated; or from finishing hydrated lime wet into a paste and allowed to stand for 24 hours before Plaster of Paris is incorporated; hydrated lime shall be sieved into a watertight box three-quarters full of water. A small portion of white sand shall be added te lime putty before plaster of Paris is incorporated* She sand may be added while quicklime is being slaked or to hydrated lima#while being eieved into water. Director of Bureau of Standards -3- Sept eu.be r 19, 1928 "Keene's Cement Plaster. -- The walls of the pupils' stair enclosures, except where otherwise specified, shall be plastered 2 coats. Both the brown and finished coats shall be of Keene's cement mixed and applied in accordance with the manufacturer's directions. The finished coat shall be troweled to a hard, smooth, polished surface. ' "PLASTER WALLS. -- All plaster walls shall be painted 3 coats unless otherwise specified. "The first coat or primer shall be a semi-gloss pigment primer which has lime resisting properties. It shall be applied in accordance with the printed instructions of the manufacturer and shall not be recoated until it has dried hard and absolutely free from ta.cl. Succeeding coats of paint shall not be applied until the priming has been inspected and approved by the Superintendent. "The second coat, except v;here otherwise specified shall be lead and oil paint. "The third coat, except where otherwise specified, shall be lead and oil paint with an eggshell finish." Thanling you in advance for your assistance in this matter, I am Very truly yours. WALTER c. ilARTIR, Architect, Superintendent of School Buildings.