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1、BRITISH STANDARD BS 7779:1994 Specification for Semi-transparent priming stains (stain basecoats) for joinery UDC 667.74:667.638.2 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:48 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7779:1994 This British Stand
2、ard, having been prepared under the direction of the Materials and Chemicals Sector Board (I/-), was published under the authority of the Standards Board and comes into effect on 15 January 1995 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference STI/28
3、Draft for comment 93/508113 DC ISBN 0 580 23251 4 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Materials and Chemicals Sector Board to Technical Committee ST1/28, upon which the following bodies were represented: British Cement Associ
4、ation British Coatings Federation Ltd. British Decorators Association Department for Education Department of the Environment Department of the Environment (Building Research Establishment) European Resin Manufacturers Association Furniture Industry Research Association Ministry of Defence Oil and Co
5、lour Chemists Association Paint Research Association Society of Chemical Industry Timber Research and Development Association Titanium Pigment Manufacturers Technical Committee Union of Construction, Allied Trades and Technicians The following bodies were also represented in the drafting of the stan
6、dard, through subcommittees and panels: British Wood Preserving and Damp-proofing Association British Woodworking Federation Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:48 GMT+00:00 2006, Uncontr
7、olled Copy, (c) BSI BS 7779:1994 BSI 09-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2References1 3Definitions1 4Classification1 5Sampling1 6Composition1 7Performance requirements1 8Marking of containers2 Annex A (normative) Test for resistance to natural weatherin
8、g3 Annex B (normative) Test for recoatability after natural weathering4 Annex C (normative) Test for blister resistance5 Figure B.1 Test panel with water trap4 Figure B.2 Diagram showing zone A and zone B areas in which cracking from water trap on overcoated natural weathering panels is assessed5 Fi
9、gure C.1 Details of a suitable blister box for blister resistance test7 List of referencesInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:48 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7779:1994 ii BSI 09-1999 Foreword This British Stan
10、dard has been prepared under the direction of the Materials and Chemicals Sector Board as a companion standard to BS 5082 and BS 5358. It is intended primarily for factory-applied priming stains applied to softwood joinery, and which may be overcoated subsequently with finishing coats of paints or s
11、tain. Whenever possible the test requirements for this specification have been aligned with those of BS 5082 and BS 5358. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance wi
12、th a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had am
13、endments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:48 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7779:1994 BSI 09-19991 1 Scope This British Standard specifies
14、requirements for priming stains for softwood joinery as defined in BS 6952-1. They are suitable when overcoated with either paint or stain finishing coats for interior and exterior use. NOTEPriming stains conforming to the requirements of this specification may be suitable for use on hardwoods, but
15、the user is advised to consult the manufacturer in each individual circumstance. 2 References 2.1 Normative references This British Standard incorporates, by dated or undated reference, provisions from other publications. These normative references are made at the appropriate places in the text and
16、the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this British Standard only when incorporated in the reference by amendment or revision. For undated references
17、, the latest edition of the cited publication applies, together with any amendments. 2.2 Informative references This British Standard refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the insi
18、de back cover, but reference should be made to the latest editions. 3 Definitions For the purposes of this British Standard, the definitions given in BS 2015 apply. 4 Classification The priming stains specified in this standard shall be classified as follows. a) Type A. An industrial priming stain f
19、or factory application by dipping, deluging, flow coating, spraying or other mechanical process. NOTE 1It will normally be applied to wood treated with one of the preservatives recommended in BS 5589. b) Type B. A priming stain for site application by brush. NOTE 2For optimal exterior performance th
20、e priming stain should be applied to wood pretreated with a preservative recommended in BS 5589. NOTE 3The test requirements specified in this standard for the two types of priming stain are identical. Users will need to confirm with the paint manufacturer that the application, storage and drying pr
21、operties of type B products are suitable for the intended end use. 5 Sampling For the purposes of the tests specified, a representative sample of the priming stain measuring not less than 500 ml shall be taken and packed by the method described in BS 3900-A1. A container of glass or other non-corrod
22、ible material shall be used. 6 Composition The priming stain shall be based on a pigmented solution or dispersion of polymeric material in a water or organic solvent carrier. The priming stain shall not contain materials which may migrate from it and cause discoloration when overcoated with solvent-
23、 or water-thinned paint or stain finishes. NOTECompatibility with glazing compounds and systems should not be assumed and should be discussed with glazing suppliers or manufacturers. 7 Performance requirements 7.1 Appearance When the priming stain is applied, by the method recommended by the manufac
24、turer, to the planed surface of a European redwood panel (Pinus sylvestris) of not less than 300 mm 100 mm and then allowed to dry in a vertical position as recommended by the manufacturer, the film shall be smooth and of uniform appearance, free from runs and sags, and the grain of the wood shall b
25、e visible. 7.2 Resistance to natural weathering The priming stain, applied and tested in the manner described in Annex A, shall not show at the end of the 3 month exposure period cracking, flaking or surface mould, and there shall be no evidence of wood splitting. The colour change shall be no great
26、er than 5 %E units as given in BS 3900-D8. 7.3 Overcoatability after natural weathering When the test panels, prepared and exposed to natural weathering as described in Annex A, are tested as described in Annex B, none of the panels shall show signs of defect either during recoating or after drying.
27、 At the end of the 9 month exposure period none of the panels shall show blistering. There shall be no cracking of the timber or coating in areas removed from the water trap and cracking from the water trap shall be confined to no more than four cracks in zone B in Figure B.2. Flaking, adhesion, and
28、 surface mould growth shall be rated not greater than 1 (see Annex B). 7.4 Blister resistance When the priming stain is tested by the method described in Annex C, no blistering or cracking shall be evident. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:4
29、8 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7779:1994 2 BSI 09-1999 8 Marking of containers Each container shall be permanently and legibly marked with the following information: a) the manufacturers name, trademark and product designation; b) the batch number and/or date of manufacture; c) the
30、number and date of this British Standard i.e. BS 7779:1994; d) the method of application and the recommended spreading rate expressed in square metres per litre; e) the thinners to be used, if required. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:48 GM
31、T+00:00 2006, Uncontrolled Copy, (c) BSI BS 7779:1994 BSI 09-19993 Annex A (normative) Test for resistance to natural weathering A.1 Materials A.1.1 Wood The panels shall be made from straight grained European redwood or home-grown Scots pine of normal growth rate (8 to 20 annual growth rings/25 mm)
32、 free from knots, shakes, resinous streaks, visible blue fungal stain, evidence of surface or bulk fungal infection and abnormal porosity due to bacterial attack during storage. NOTEAbnormal porosity may be detected qualitatively by the rapid absorption of a drop of propan-2-ol applied to a smooth s
33、urface; the drop should not be absorbed in less than 30 s by wood of normal porosity. The test should be carried out at not less than six widely separated places on the test panel. The wood shall be conditioned at a temperature of (23 2) C and relative humidity of (50 5) % until the equilibrium mois
34、ture content of the wood is (12 2) % r.h. Any wood showing surface splitting at this stage shall be rejected. A.1.2 Panels The panels shall be cut from flat sawn boards planed all round to approximately 375 mm 120 mm 20 mm, then machined to a smooth uniform finish. In order to achieve a clean finish
35、 to the end-grain and to eliminate any tearing of the fibres arising during cross-cutting, the following procedure shall be used. a) Flat-cut and thickness the wood to approximately 2 mm above the final thickness. b) Cross-cut using a well sharpened and dressed tungsten carbide tipped circular saw.
36、c) Carry out final surfacing of the test face on an overhand planer. d) Do not carry out further preparation, e.g. smoothing with abrasive paper or cloth. A.1.3 Selection Select the panels carefully to give a sapwood test surface on the convex side of the growth rings, with any heartwood confined to
37、 a band not exceeding 5 mm when measured from the rear face. If the presence of heartwood in the selected timber cannot be detected by a difference in colour in the wood (heartwood is darker), it shall be checked by the brush application of a test solution to both the end-grain and the faces of a sm
38、all piece cut from the same length of wood. The test solution shall be prepared by dissolving 20 g of o-anisidine (see warning note) in 35 ml of concentrated hydrochloric acid (d 1.18 g/ml) and then diluting to 2 l with water. Before use, this solution shall be diluted with an equal volume of a 10 %
39、 (m/m) aqueous solution of sodium nitrite. Heartwood, if present, is indicated by the development of a deep red colour which usually shows in about 10 min 1. WARNING NOTE. O-anisidine is classified as very toxic by inhalation, in contact with the skin and if swallowed; there is evidence that it is a
40、 possible carcinogen. A.2 Procedure A.2.1 Application of priming stain Prepare five panels for each priming stain under test. Mask off a section 50 mm from one end and 25 mm from the other end, and apply the priming stain to both faces and edges by a technique specified by the manufacturer to achiev
41、e the recommended spreading rate. Allow to dry in a vertical position with free access of air at a temperature of (23 2) C and a relative humidity of (50 5) % for 4 days. Remove the masks, and seal the faces, edges and end-grains of the unpainted strips at the end of each test panel using a suitable
42、 sealing paint, e.g. a paint conforming to BS 4756, which should be contiguous with, but not overlapping, the test priming stain. Allow to dry for a further three days. A.2.2 Exposure Four of the five panels shall be exposed with the broad band of the sealant on the left hand side in accordance with
43、 BS 3900-F6, with the long edge horizontal and the convex side of the growth rings outermost, for a period of 3 months. Commence the exposure in the period 1 May to 30 September and expose at an angle of 45, facing the equator. The remaining panel shall be retained as a control under laboratory cond
44、itions at a temperature of (23 2) C and relative humidity of (50 5) % and in the dark. A.2.3 Examination After the 3 months exposure period, remove the test panels from exposure and condition for 24 h at a temperature of (23 2) C and relative humidity of (50 5) %. Examine the priming stain for film
45、defects and wood cracking using a magnification of 10. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:39:48 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7779:1994 4 BSI 09-1999 Wash the panels by sponging with clean lukewarm water to remove surface deposits
46、 of atmospheric pollutants and allow to dry. Assess colour change against the retained panel in accordance with BS 3900-D8, BS 3900-D9 and BS 3900-D10. Annex B (normative) Test for recoatability after natural weathering B.1 Materials B.1.1 Panels Panels shall be washed and dried after the inspection
47、 following initial exposure of the priming stain (A.2.3), and equilibrated at a temperature of (23 2) C and relative humidity of (50 5) % until the moisture content of the wood is (12 2) %. B.1.2 Finishing systems Finishing systems shall comprise an undercoat and white finishing paint (conforming to
48、 BS 7664) and a semi-transparent exterior wood stain classified as medium build in BS 6952-1 and medium brown in colour. B.2 Procedure B.2.1 Overcoating Apply one further coat of sealer (A.2.1) to the sealed ends of the panels. Ensure that the sealer is contiguous with, but not overlapping, the test
49、 priming stain. Allow to dry for (20 4) h. Apply one coat of undercoat to the weathered face and edges of two panels and one coat of medium build exterior wood stain to the weathered face and edges of two panels. Leave to dry for (20 4) h. Then apply one coat of alkyd gloss and one coat of medium build exterior wood stain to the appropriate panels. Ensure that the finishing systems are contiguous with, but not overlapping, the end sealer, and apply each coat at the manufacturers recommended covering rate. Allow to dry at (2
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