RESIST PRINTING UNDER REACTIVE DYES REIST PRINTING: PREVENTION OF DYE FIXATION AT THE PRINTED PORTION WHITE RESIST: WHITE PRINT AGAINST COLOURED BACKGROUND COLOURED RESIST: COLOUR PRINT AGAINST COLOUR BACKGROUND PRINCIPLE REACTIVE DYES FIXED ON COTTON UNDER ALKALINE CONDITIONS DYE FIXATION PREVENTED UNDER ACIDIC CONDITIONS SEQUENCE: PRINT WITH RESISTING AENT > DRY > NIP PAD WITH DYE + ALKALI >DRY > STEAM > WASH > SOAP > WASH > DRY

CHOICE OF ACID INORGANIC ACID SUCH AS HCl NOT SUITABLE DUE TO DANGER OF FIBRE DEGRADATION DURING STEAMING VOLATILE ORGANIC ACID LIKE ACETIC ACID NOT SUITABLE NON-VOLATILE ORGANIC ACID LIKE CITRIC ACID, TARTARIC ACID SUITABLE THICKENER: SHOULD BE STABLE TO ACID e.g. MODIFIED GUAR GUM (INDALCA AGBV)

PRINT PASTE COMPOSITION CITRIC ACID 50 PARTS WATER 50 ml THICKENER PASTE 900 PARTS TOTAL 1000 PARTS PRINT > DRY PAD LIQUOR COMPOSITION REACTIVE DYE 10-20 g/l RESIST SALT 10 g/l SOD. BICRBONATE 10-20 g/l NIP PAD > DRY > STEAM FOR 10-15 MIN. > WASH > SOAP > WASH > DRY

COLOURED PRINT AGAINST COLOUR BACKGROUND COLOURED RESIST COLOURED PRINT AGAINST COLOUR BACKGROUND PRINCIPLE: INCORPORATE DYE/PIGMENT IN RESIST PASTE WHICH CAN BE FIXED UNDER ACIDIC CONDITION SIMULTANEOUS FIXATION OF GROUND COLOUR AND PRINT COLOUR PIGMENT ALONG WITH BINDER MOST SUITABLE PRINT PASTE COMPOSITION PIGMENT COLOUR 20-30 PARTS BINDER 100 PARTS EMULSION THICKENER 850 PARTS CITRIC ACID 50 PARTS TOTAL 1000 PARTS PRINT > DRY > NIP PAD WITH REACTIVE DYE + ALKALI > DRY > STEAM > WASH > SOAP > WASH > DRY

DISCHARGE PRINTING UNDER REACTIVE DYES PRINCIPLE DISTRUCTION (CHEMICAL DECOMPOSITION) OF DYE AT THE PRINTED PORTION DISCHARGING AGENT THERMALLY STABLE STRONG REDUCING AGENT COMMON DISCHARGING AGENTS SODIUM SULPHOXYLATE FORMALDEHYDE (HSO2CH2O)Na OR ZINC SULPHOXYLATE FORMALDEHYDE (HSO2 CH2O) 2 Zn OR Zn(OH)(HSO2CH2O) (HSO2CH2O)Na + H2O > CH2OHSO3NA + 2 H TRADE PRODUCTS ROGALITE C (BASF), SAFOLITE (TRANSPEK), AROSIT SR (CLARIANT)

DISCHARGING AGENTS CALCIUM SULPHOXYLATE FORMALDEHYDE ( RONGALIT H) STANNOUS CHLORIDE THIUREA DIOXIDE

SEQUENCE UNDYED FABRIC > DYEING > DISCHARGE PRINTING > DRY > STEAM > WASH > SOAP > WASH > DRY GROUND COLOURS CORRECT CHOICE OF DYES IS VERY IMPORTANT IN DISCHARGE PRINTING SUITABLE DYES USUALLY CONTAIN N=N GROUP WHICH IS READILY ATTACKED BY REDUCING AGENTS GIVING COLOURLESS WATER SOLUBLE AMINES R-N==N-R’ > RNH2 + R’NH2 INFORMATION RELATED TO EASE OF DISCHARGEABILITY IS NORMALLY GIVEN IN MANUFACTURERES SHADE CARDS

COLOURED DISCHARGE DYES STABLE TO REDUCING AGENT AND THOSE CAN BE FIXED DURING STEAMING IN PRESENCE OF REDUCING AGENT ARE INCORPORATED IN DISCHARGE PASTE VAT DYES ARE MOST SUITABLE

WHITE DISCHARGE GLYCERINE 10-20 PARTS REDUCING AGENT 30-150 PARTS ZnO/TiO2 30-50 PARTS WATER 100-150 PARTS OPTICAL BRIGHTENER 10 PARTS BRITISH GUM TO MAKE 1000 PARTS THIKENER PASTE PRINT ON DYED FABRIC > DRY > STEAM FOR 30 MIN > WASH > SOAP > WASH > DRY

COLOUR DISCHARGE VAT DYE 50-100 PARTS Na2CO3/K2CO3 30-40 PARTS Zn/Na SULPHOXYLATE FORMALDEHYDE 80-120 PARTS GLYCERINE 10-20 PARTS WATER 100-150 PARTS BRITISH GUM THICKENER PASTE TO MAKE 1000 PARTS PRINT ON DYED FABRIC > DRY > STEAM 30 MIN. > WASH > OXIDIZE > WASH > SOAP > WASH > DRY