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Pigment Garment Dyeing Using Cold Water
Although the pretreatment phase of pigment dyeing is the same on all machines, the actual dyeing procedure varies greatly between machine types. This procedure sheet is broken down into two steps to help simplify your getting started. Because of the dye procedure variation over a range of machines, this procedure sheet will only cover top loading and front loading rotary machines. If more information is required, please contact the 941-946-3131 for more help.This information is offered in only the broadest sense, and is intended to assist in the initial stages of setup and the learning about pigment garment dyeing
Pretreatment of Goods
Basics: Pigment dyeing is an electrical process whereby the goods to be dyed are given an electrical charge opposite that of the pigment. When the pigment is added to the bath, the opposite electrical charges attract each other, much like the north and the south poles of two magnets. Because of the electrical nature of the process, it is very important not to mix dissimilar fabrics in the same dye bath. Also important is the quality of finish on the goods. Normally a good nonionic softener is preferred as the finish. If a cationic softener is on the goods, it reduces the pickup of pretreat and likewise a strong anionic softener will cause the pretreat to be neutralized or cause an uneven exhaust. For reference, pretreats are all cationic and pigments vary from nonionic to anionic. It should be understood that the application of softener on the piece goods must be applied evenly for this process to work. If there is any doubt on softener or softener application, the garments should be prescoured to remove the finish.
1. Fill machine with goods to be pretreat and start. Fill to a water level allowing for a liquor ratio of no more than 20/1.
2. Start machine and allow to run until goods are
well saturated with water and evenly dispersed in the tub.
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3. For normal pigment strengths of up to 12%, a 6% pretreatment based on weight of goods should be all that is needed. It should be noted that pretreats are very susceptible to high amounts of chlorine in the water. Anytime your chlorine exceeds .6 PPM, it may be necessary to add additional pretreat. Our recommended procedure calls for a small portion of the binder to be added during the pretreatment cycle. This is not mandatory, but it seems to improve washfastness on the final product. If you choose to use this process, it is referred to as the Double-Resin Method. The amount of Uni-Rez to use at this time is 4% on weight of goods.
4. Run the machine for 15 minutes, dump, and extract until near dry. Normally this length of time is adequate to allow for maximum pickup of pretreat and binder. If you have excessive problems exhausting your dye bath, it may be because of insufficient pretreat pickup. This can be resolved in one of three ways. Prescouring the goods will increase the anionic charge allowing for better pickup, running the machine longer during pretreatment, or the addition of a water hardener such as magnesium sulfate (Epsom salt) to raise the water hardness up to the 15 grain range. All of these methods have had varying success in different applications. You will have to try each to see which will work best for you. A simple test for residual pretreat in the bath is to take a sample of bath water (100 grams) and slowly add one drop at a time of Dioctal Sulpho Succinate while stirring. Because the precipitation reaction is so great due to the different electrical charges, when near equal amounts are added, the sample will turn hazy. From this you can calculate the approximate pickup of pretreat on any given bath.
5. Assuming that all has gone well, you should be ready to go on to the actual dyeing stage of the process.
Application of Pigment to Pretreated Goods
Basics: The application of pigments through exhaust dyeing is a relatively new process. As already stated, this is an electrical process that requires exact duplication from one dye lot to the next if you are to maintain consistency of color and shade. Our pigments are specially formulated to be applied in cold water applications and should not be compared to standard printing pigments used to textiles. Although heat is not required for the complete application of our pigments, some clients seem to feel that the yield is improved when it is used. There is a technical reason for this that does not apply here, but, if you need to know, then call us and we will be happy to explain the reason. As with most conventional dye products, the use of an electrolyte greatly eases the application of color. Our pigments have been enhanced to be susceptible to the commonly used electrolytes and will completely exhaust in cold water. The most common electrolyte used in pigment dyeing is Acetic Acid. This is normally diluted into a 10% solution for better control of exhaustion. Anionic pigments do not exhaust on a straight line. This is important to remember when adding acid. A pigment will reach a breakover point at which a small acid add will show a major change in the exhaustion. If too much acid is added too fast at this point, then depending on electrolyte imbalance, it will either slam on unevenly or it will pickle. The term pickle refers to creating an electrolyte imbalance which causes the pigment to lose affinity for the goods. This pickling usually appears as a precipitation in the dye bath and in extreme cases will actually start to remove already exhausted pigments. Often times the pickling effect can be neutralized by addition of bicarbonated soda, bringing the bath Ph back up to 6.5 or more. After raising the Ph, continue on with the exhaustion. Most of our pigments will start to exhaust at a Ph level of around 6.5, and will be fully exhausted by Ph 4.7. These are guidelines and not absolutes. These Ph levels assume a liquor ratio of less than 10/1 with a water hardness in the range of 5.5 to 7.5 grains. Soft water is detrimental to the exhaustion of pigments and should be avoided whenever possible. If soft water is unavoidable, then it can be hardened using magnesium sulphate or calcium carbonate to achieve the desired hardness. Likewise, if your water is exceptionally hard and causing uneven dyeing, EDTA 40% solution may be used as a sequesterant to reduce hardness. CAUTION SHOULD BE USED WITH THE ADDITION OF EDTA! Usually an amount equal to .0005 to .001 of water volume is all that you will need. Too much and the bath will never exhaust. One final note of importance, our pigments are similar to dyestuffs in that the process is controlled not only by electrolyte but also liquor ratio and water hardness.
Dyeing of Goods
Abbreviations: OWG-on weight of goods TL-top loading machine SL-side loading machine
1.-TL Remove pretreated goods from machine and place to side. Fill and rinse machine twice. After rinsing machine, fill with water to a level of not more than 20/1 liquor ratio to goods. Start machine.
1.-SL Fill machine with water and start. As stated, preferred liquor ratios are 10/1 or less.
2.-TL Add the desired amount of color to the running machine. If you are going to reuse the bath, then add an additional 35% color to machine.
2.-SL In a separate container, mix the appropriate amount of dye with at least three parts of water and mix thoroughly. After mixing, slowly add the dye solution to running machine over a 10 minute period. This can be adjusted as needed after you are more familiar with the process.
3.-TL Rapidly add the pretreated garments to the running machine. When all garments have been added, reset the timer to maximum allowed running time at normal agitation.
3.-SL After the machine has run for 5 minutes, add the binder. For normal colors (10%) this is usually 5% OWG with the Double-Resin Method or 10% OWG without.
4.-TL If you intend to exhaust the bath with acid, then make a 5% solution of acetic acid at this time. Also add the appropriate amount of binder for the method of choice. It should be noted that to exhaust in a top loader is not recommended because of the slow agitation these machines have. For one or two piece samples, this machine does quite well with the exhaust method, but more goods can become difficult to control. To exhaust using this machine, you will have to reset the timer to avoid early drain and extract. If you are reusing the bath, then make sure your drain hose is attached to at least a 30 gallon container.
4.-SL After machine has run 15 minutes, add l% OWG of the 10% acid solution to the machine. Note the minutes until bath clears or until a Ph reading below 4.1 is noted. Certain pigment formulas require no acid for exhaustion. If noticeable exhaustion occurs before your first acid add, it will probably be wise not to add any acid and watch the bath. When exhaustion stops, start your acid adds. If total exhaustion occurs with no acid adds, then it is still necessary to add 3-5% OWG Ph 10% solution at the end and run for at least 5 minutes to lock the color in place.
5.TL- If you are reusing the bath, then at the end of your first cycle, dump the machine and very lightly extract. This is the point that most problems arise for the garments. When the machine goes into extract, it should not run more than 5 seconds. Stop the machine after all water is out of the tub, flip the garments over, and extract 5-10 seconds more. If done properly, the garments will still be dripping wet. Place in dryer and run until dry on high heat. If you choose to exhaust your garments, then start adding 10 Grams of 5% acid solution every 5 minutes until the bath is fully exhausted or a Ph of 3.8 is noted.
5.-SL If proper exhaustion has occurred, then you can do a normal extraction and drying process as you would for any dyed goods. Because the chosen electrolyte evaporates in the dryer, it is not normally necessary to rinse the goods. For problem resolution, please contact us.
6.-TL If you have chosen to exhaust your bath, then dump and extract in a normal manner. Rinsing is not necessary.
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Copyrighted 1998 by Quality Dye Works Inc. Last Updated March 30, 2009
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