Method and apparatus for controlling dissolved solid concentrations

A method and apparatus are provided for controlling the concentrations of dissolved solids in a plurality of solutions contained in a plurality of interconnected baths. The conductivities of the solutions are monitored and make-up liquid is added to each bath when the conductivity of the respective solution exceeds a predetermined level.

The present invention relates to rinsing systems and more particularly to a 
system for maintaining optimal concentrations of dissolved solids in a 
plurality of interconnected rinsing baths. 
There are many industrial applications in which products are treated with a 
solution, e.g. a bleach, a dye, a finish or an acid. After a selected 
period of time, the treating solution must be removed to avoid damaging 
the product or before a further manufacturing step can be performed. 
Typically, the product is sequentially rinsed in a plurality of baths to 
remove the initial treating solution. The products are frequently rinsed 
on a continuous basis, in contrast to a batch basis. The rinsing solutions 
contained in the baths are regularly replenished because otherwise the 
concentrations of the solutions gradually change until they fail to remove 
all of the process solution from the products. 
Although the systems are generally run on a continuous basis, the 
conditions of the product and the baths are not static. For example, there 
are often irregular variations over time in the amount of solution carried 
into the baths by the products. As a result, the concentrations of the 
baths vary in an unpredictable fashion. In order to overcome these 
unpredictable variations, which often lead to defective products, it is 
common to overcompensate in the replenishment of the baths with fresh 
rinsing liquid. This overcompensation leads to an obvious waste of rinsing 
liquid. Moreover, if the liquid is heated or cooled, there is a 
consequential waste of energy, an undesirable expense. 
One example of such a rinsing system is used in the manufacture of certain 
textile products, in which a continuous web of fabric is bleached with an 
alkaline solution, such as sodium hydrosulfite and/or other chemical 
additives. However, the bleaching solution is promptly rinsed from the 
fabric in order to avoid yellowing or other damage to the fabric. 
Similarly, in dye rinsing and finishing operations, the process solutions 
are promptly removed from the material. 
In a typical fabric rinsing system, after the web is treated with a process 
solution, it is successively immersed in a plurality of interconnected 
rinsing baths, for example four rinsing baths. The four rinsing baths 
contain rinsing solutions which are successively diluted, i.e. the first 
bath is the most concentrated with chemical additives and the fourth bath 
is the least concentrated with chemical additives, essentially chemical 
free. This successive dilution is accomplished by adding fresh water to 
the fourth bath, running a countercurrent flow from the fourth bath to the 
first bath, and then discharging the water and chemical additive solution 
from the first bath for waste treatment and/or disposal. 
After the fabric has been bleached, dyed or otherwise chemically treated, 
it is directed into a first rinse bath where an initial portion of the 
chemicals are rinsed from the fabric solution. A portion of the chemical 
additives is removed from the fabric to remain in the first bath. The 
fabric thus exits from the first bath carrying a first diluted solution. 
Thereafter, the fabric is sequentially immersed in the second, third and 
fourth baths, each of which removes an additional portion of the chemical 
additives. As the fabric exits from the fourth bath, it is substantially 
free of the chemical additives. However, the pH may be unacceptable, 
either high or low, and require further adjustment. 
In some instances, where the solution carried by the product is alkaline, 
it is then immersed in an appropriate pH bath, for example, acetic acid, 
to neutralize the slight alkalinity of the solution carried by the web 
after exit from the fourth bath. In other operations, the product may 
carry an acidic solution and require alkaline neutralization in a similar 
manner. This final immersion is intended to ensure that there is no 
residual alkalinity or acidity in the fabric, other than as desired. 
In order for the fabric to emerge from the pH control bath in the desired 
condition, there is an optimal concentration of chemical and mineral salts 
for each of the baths and an optimal pH for the pH bath. 
If the fabric web were run absolutely continuously at a constant speed 
through the rinsing baths, if the initial bleaching solution were 
maintained at a constant concentration, if the web always carried a 
constant amount of solution per running foot of web, and if the web was 
always the same width and weight, then the optimal bath concentrations and 
pH could probably be maintained with merely a constant input of fresh 
water into bath four and a constant input of pH adjustment chemical and 
water into the pH bath. However, such ideal conditions do not exist in an 
operating plant. Instead, the web speed varies, the concentration of the 
initial chemical solution varies and the amount of solids carried by the 
fabric varies with the particular weave and the varying character of the 
yarn. Each of these variations contributes to overall changes in the 
concentrations of the baths, i.e., deviation from the optimal 
concentrations. Consequently, constant inputs of fresh water and pH 
adjustment chemical cannot maintain the optimal concentration. These 
deviations accumulate and, over time, lead to substantial changes in 
concentrations and a decline in product quality. 
As noted above, heretofore it has been standard practice to merely 
overcompensate for possible deviations, adding excess fresh water and 
excess pH adjustment chemical. Manual checks are occasionally made to see 
whether the final product is too alkaline or too acidic and suitable 
manual adjustments are made. This procedure does not lead to a uniform 
product because several variations can occur between testing, and the 
variations are not detected until it is too late to remedy the situation. 
The product is already damaged. It is not uncommon for a bleaching dying 
or finishing plant to have a rejection rate as high as 30%. 
In addition to the tremendous losses caused by defective products, the 
overcompensation of fresh water and pH adjustment chemical is also 
expensive. The additional costs of overcompensation occur in at least 
three forms. First, there is the added cost of the wasted materials 
comprised of water and pH adjustment chemical. Secondly, there are 
additional fuel expenses because the rinsing baths are generally 
maintained at elevated temperatures, for example, between about 
120.degree. F. and 180.degree. F. Any excess water added to the baths 
constitutes a waste of the fuel used to heat it as input water is 
approximately 55.degree. F. prior to heating. Thirdly, all of the solution 
exiting from the first bath must be treated before it can be disposed. 
Excess solution requires excess equipment capacity as well as additional 
treating materials. These excess costs caused by overcompensation are 
substantial in some operations. 
It is therefore an object of the present invention to provide a system for 
continuously monitoring and maintaining generally constant concentrations 
of a plurality of interconnected rinsing baths. It is also an object to 
provide a system for minimizing the waste of materials and fuel in a 
rinsing system. It is a further object to improve the quality and 
uniformity of products exiting from a plurality of interconnected rinsing 
baths.

The conductivity of a solution of dissolved solids is proportional to the 
concentration of dissolved solids. That is, an increase in concentration 
results in a corresponding increase in conductivity. Consequently, if a 
solution is maintained at a generally constant conductivity, the 
concentration of dissolved solids also remains generally constant. 
In accordance with the present invention, at least two baths, a first bath 
and a second bath containing a first rinsing solution and a second rinsing 
solution, respectively, are connected in flow communication with one 
another, with the first solution flowing into the second bath. The product 
being rinsed flows counter to the solution flow. The first rinsing 
solution is diluted with a make-up liquid to a greater degree than the 
second rinsing solution. First conductivity monitoring means are placed in 
contact with the first solution contained in the first rinsing bath. The 
first conductivity monitoring means are operatively connected to a first 
valve means controlling the flow of make-up liquid from a make-up liquid 
source into said first bath. Second conductivity monitoring means are 
placed in contact with the second solution contained in the second rinsing 
bath. The second conductivity monitoring means are operatively connected 
to a second valve means controlling the flow of make-up liquid from the 
make-up liquid source into said second bath. The first conductivity 
monitoring means and the second conductivity monitoring means are 
interconnected so that the second conductivity monitoring means is 
prevented from opening the second valve means to dilute the second rinsing 
solution with a make-up liquid unless the first valve is simultaneously 
open to admit make-up liquid from the make-up liquid source into the first 
bath. 
Referring more particularly to the drawings, in the depicted embodiment, a 
system is provided for rinsing a continuous fabric web 10 to remove an 
initial bleaching solution. The system includes four successive alkaline 
rinsing baths 12, 14, 16 and 18 and a neutralizing acid bath 20. Each of 
the baths 12, 14, 16, 18, and 20 contains a rinsing solution 22, 24, 26, 
28 and 30, respectively. A plurality of conventional directing rollers 32 
are located adjacent to and within each of the baths 12, 14, 16, 18, and 
20 to direct the fabric web 10 over a path of successive immersion in the 
baths 12, 14, 16, 18 and 20, prior to drying and rolling for storage or 
further processing. 
The baths 12, 14, 16 and 18 are sequentially interconnected to provide flow 
communication between successive baths. In the depicted embodiment, flow 
communication is provided by means of overflow discharge from the bath 18 
to the bath 16, from the bath 16 to the bath 14, and from the bath 14 to 
the bath 12. Make-up liquid is continuously added to the bath 18 from a 
fresh water source 34 through the valve 37 at a predetermined rate. The 
rate of flow through the valve 37 is set to maintain a minimum solution 
overflow from tank 12. Thus, when the baths are full, and water is added 
to the bath 18, there is an overflow discharge of solution 28 into the 
bath 16, of solution 26 into the bath 14, and of solution 24 into the bath 
12. In addition, there is a final overflow discharge of the solution 22 
from the bath 12. The overflow discharge from each of the baths 10, 12, 
14, and 16 ensures that there is a maximum volume of rinsing solution in 
each of the rinsing baths. 
The bath 20 is not interconnected with the baths 12, 14, 16 or 18. Instead, 
a constant input of dilute acid is provided and an overflow discharge 
maintains a constant volume of solution 30 in the bath 20. 
Each of the baths 12, 14, 16, 18 and 20 is provided with conductivity 
monitoring means, each of which includes an electrode sensor 52, 54, 56, 
58 and 60, respectively. Each electrode sensor comprises a 1 volt 
alternating current, carbon-tipped, temperature-compensated electrode. 
The electrode sensor 52 is in constant contact with the solution 22 in the 
bath 12. The sensor 52 is electrically connected to a controller 62 which 
includes a meter 72 and an optional recorder 82 adapted for continuous 
display and recording of the conductivity of the solution 12. As noted 
above, the conductivity of the solution 22 is proportional to the 
concentration of dissolved solids. Thus, the recorder 82 provides a 
continuous record of the mineral salts concentration of the first solution 
22. Similarly, each of the baths 14, 16 and 18 is provided with a sensor 
54, 56 and 58, respectively, and each of the sensors 54, 56 and 58 is 
electrically connected to a controller 64, 66 and 68 respectively. Each of 
the controllers 64, 66 and 68 includes a meter 74, 76 and 78, 
respectively, and includes an optional recorder 82, 84 and 86, 
respectively. Thus, there is provided a continuous record of the 
conductivity, and thus dissolved solids or mineral salts concentrations, 
of all of the solutions 22, 24, 26 and 28. 
The controller 68, which monitors the solution 28 is electrically connected 
to the solenoid valve 36 which controls the flow of fresh make-up water 
from the water source 34 to the bath 18. Whenever the conductivity of the 
solution 28 exceeds a predetermined control point for the solution 28, the 
controller 68 opens the solenoid valve 36 to add additional fresh water to 
the solution 28, thus reducing the concentration and conductivity of the 
solution 28 to a level which yields an acceptable final product. 
The controller 66 is electrically connected to a solenoid valve 92 which 
controls the flow of the fresh water from the source 34 to the bath 16. 
When the conductivity of the solution 26 exceeds a predetermined control 
point for the solution 26, the solenoid valve 92 is opened to add fresh 
water to the bath 14. 
Similarly, the controller 64 is electrically connected to a solenoid valve 
94 which controls the flow of fresh water from the source 34 to the bath 
14. When the conductivity of the solution 24 exceeds a predetermined 
control point for the solution 24, the solenoid valve 94 is opened to add 
fresh water to the bath 14. 
Also, the controller 62 is electrically connected to a solenoid valve 96 
which controls the flow of fresh water from the source 34 to the bath 12. 
When the conductivity of the solution 22 exceeds a predetermined control 
point for the solution 22, the solenoid valve 96 is opened to add fresh 
water to the bath 12. 
The solenoid valves 36, 92, 94 and 96 are electrically interconnected with 
one another by means of a double-pole-double-throw relay 98, built into 
each of the controllers 62, 64 and 66 such that the valve 92 cannot be 
opened unless the valve 36 is open, the valve 94 cannot be opened unless 
the valves 36 and 92 are open and the valve 96 cannot be opened unless the 
valves 36, 92 and 94 are open. In this manner, fresh water is not added to 
any "downstream" bath as long as the "upstream" solutions are below the 
predetermined conductivity control points for those solutions. As a 
result, there is a large reduction in the amounts of water and fuel used 
in the process. 
The conductivity sensing means 50 for the acid bath 20 includes an 
electrode sensor 60 like the sensors 52, 54, 56 and 58. The sensor 60 is 
electrically connected to a controller 102 which includes a meter 104 and 
an optional recorder 106 adapted for continuous display of the 
conductivity of the solution 30. The conductivity of the solution 30 is 
proportional to the concentration of the dissolved solids, in this case 
the bleaching solution, and the acid concentration. Thus, the recorder 106 
provides a continuous record of the total concentration of mineral salts 
in the solution 30. 
The controller 102 is electrically connected to a normally closed solenoid 
valve 114 which controls flow communication from the fresh water source 34 
into the bath 20. When the conductivity of the solution 30 exceeds a 
predetermined maximum control level, the solenoid valve 114 is opened to 
add fresh water to the bath 20. As noted above, overflow discharge means 
are provided in the bath 20 to maintain a constant volume of solution 30 
in the bath 20. 
Means are also provided for sensing and controlling the pH of the solution 
30. The pH sensing means includes a pH probe 108, such as Model P60L-3-l 
available from Great Lakes Instrument Co. of Milwaukee, Wis., and a pH 
analyzer 110, such as Model A70-0-1-0-8, also available from the Great 
Lakes Instrument Co. of Milwaukee, Wis. The probe 108 is in continuous 
contact with the solution 30 and electrically connected to the analyzer 
110. The analyzer 110 is electrically connected to an optional recorder 
112 adapted for providing a continuous record of the pH of the solution 
30. The analyzer 110 provides a signal when the pH of the solution 30 
exceeds a predetermined maximum level or falls below a predetermined 
minimum level. 
The pH analyzer 110 is also electrically connected to a normally open acid 
solenoid valve 116 and to a normally closed acid solenoid valve 118. The 
valve 116 controls flow communication from an acetic acid source 120 into 
the acid bath 20. In its normally open position, the valve 116 permits an 
acid flow which is predetermined to provide optimum results under steady 
state conditions. That is, the amount of acid added to the bath 20 on a 
constant basis through the valve 116 is exactly the amount theoretically 
expected to continuously neutralize the web 10. However, as discussed 
hereinabove, the constant flow of acid does not compensate for the 
irregularities of an operating system. 
The valve 118 controls flow communication from the acetic acid source 120 
to the bath 20. When the pH of the solution 30 rises above a predetermined 
maximum level, the valve 118 is opened to add additional acid to the bath 
20 to lower the pH of the solution 30. 
When the pH of the solution 30 drops below a predetermined minimum level, 
the normally opened valve 116 is closed to stop the regular flow of acid 
to the bath 20 and the normally closed valve 114 is opened to add fresh 
water to the bath 20, thus raising the pH of the solution 30 above the 
predetermined minimum level. When the predetermined minimum level is 
reached, the valve 116 is again opened and the valve 114 is closed. 
In operation, the controllers 62, 64, 66, 68 and 102, which are 
commercially available from the Farris Chemical Company, Inc., of 
Knoxville, Tenn., under the product designation Water Mizer, continuously 
monitor the conductivity of the solutions 22, 24, 26, 28 and 30, 
respectively, and the analyzer 110 continuously monitors the pH of the 
solution 30. The conductivities of the solutions 22, 24, 26, 28, and 30 
and the pH of the solution 30 are continuously recorded by the optional 
recorders 82, 84, 86, 88, 106 and 112, respectively. 
When the conductivity of the solution 28 exceeds the control point for that 
solution, for example 280 micromhos, the controller 68 sends a signal to 
open the valve 36 to dilute the solution 28 with additional fresh water 
and reduce the conductivity thereof. The controller 68 simultaneously 
sends a signal to the relay 98 of the controller 66 to indicate that the 
valve 36 is open. When the conductivity of the solution 28 falls below the 
control point, the controller 68 causes the valve 36 to return to its 
normally closed position and halts the signal to the relay 98 of the 
controller 66. 
When the conductivity of the solution 26 exceeds the control point for that 
solution, for example 700 micromhos, the controller 66 sends a signal to 
the relay 98 of the controller 66. If the relay 98 of the controller 66 
simultaneously receives a signal from the controller 68, indicating that 
the valve 36 is open, and a signal from the controller 66 indicating that 
the solution 26 requires dilution, the relay 98 of the controller 66 is 
activated to open the valve 92 and simultaneously send a signal to the 
relay 98 of the controller 64. The valve 92 is opened to add fresh water 
to dilute the solution 26 and reduce the conductivity thereof until the 
conductivity falls below the control point for the solution 26 and the 
valve 92 is returned to its normally closed position. 
When the conductivity of the solution 24 exceeds the control for that 
solution, for example 2450 micromhos, the controller 64 sends a signal to 
the relay 98 of the controller 64. If the relay 98 of the controller 64 
simultaneously receives a signal from the relay 98, of the controller 66, 
indicating that the valves 36 and 92 are open, and a signal from the 
controller 64, indicating that the solution 24 requires dilution, the 
relay 98 of the controller 64 is activated to open the valve 94 and 
simultaneously send a signal to the relay 98 of the controller 62. The 
valve 94 is opened to add fresh water to the bath 14, diluting the 
solution 24 and reducing the conductivity thereof until the conductivity 
of the solution 24 is reduced below the control point for the solution 24. 
Then the valve 94 is returned to its normally closed position. 
When the conductivity of the solution 22 exceeds the control point for that 
solution, for example 5000 micromhos, the controller 62 sends a signal the 
relay 98 of the controller 62. If the relay 98 of the controller 62 
simultaneously receives a signal from the relay 98 of the controller 64, 
indicating that the valves 36, 92 and 94 are open, and a signal from the 
controller 62, indicating that the solution 22 requires dilution, the 
relay 98 of the controller 62 is activated to open the valve 96. The valve 
96 is opened to add fresh water to the bath 12, diluting the solution 22, 
until the conductivity of the solution 22 is reduced to a level below the 
control point for that solution. Then the valve 96 is returned to its 
normally closed position. 
Each of the controllers 62, 64, 66 and 68 includes a control light 125 
which is activated whenever the control point for the respective solution 
is met or exceeded. In addition, each of the controllers 62, 64, 66, 68 
and 102 includes an alarm light 42, 44, 46, 48, and 50 respectively. The 
alarm circuitry is designed such that, at a given conductivity level, for 
example 100 micromhos, above the respective control point, a 2 inch 
diameter alarm light is illuminated to advise the operator that the 
respective solution is above desired control by the predetermined level. 
The alarm function operates on each controller 62, 64, 66, 68, and 102 
independant of the relays 98 or of the operation of the solenoid valves. 
For example, if controller 66 goes into an alarm condition because of a 
sudden surge in the conductivity of the solution 26, the alarm light 46 is 
activated. Nevertheless, the valve 92 is opened only if the controller 68 
has signaled relay 98 and opened valve 36 as outlined above. 
In the above-described manner, substantial cost savings are achieved 
because it is not necessary to dilute the solutions 26, 24 or 22 as long 
as the upstream solutions have satisfactory concentrations of dissolved 
solids. The upstream solutions, particularly the solution 28, are better 
indicators of the quality of the web 10, the truly important 
consideration. 
Under most conditions, the automatic operation of the valves 36, 92, 94, 
and 96, is sufficient to overcome the intermittent, small changes in the 
concentrations of the solutions 22, 24, 26, and 28. That is, 
irregularities in the concentrations are usually corrected within a short 
period of time without any intervention by an operator. 
However, there are times when it becomes necessary for an operator to 
intervene in the operation, such as if there is a large, sudden change in 
the bleaching solution. In order to compensate for large changes in the 
bleach concentrations, the controller 68 is electrically connected through 
the alarm light 48 and through a time delay relay 128 to an alarm bell 
126. When the conductivity of the solution 28 exceeds the control point of 
the solution 28 by a predetermined amount, such as 100 micromhos, for 
example, the alarm light 48 is activated in turn activating the alarm bell 
126 to notify an operator that a large concentration change in the 
solution 28 has occurred. At this point the operator manually increases 
the addition of fresh water to the bath 18 through valve 37. In addition, 
the operator may activate the time delay relay 128 by switch 601 to permit 
automatic adjustment to proceed with the increased flow through valve 37 
for a predetermined period, three minutes for example. After the 
adjustment period, the alarm bell 126 is reactivated by the relay 128 if 
the conductivity of the solution has not been reduced satisfactorily in 
the intervening period. 
At the same time that the solutions 22, 24, 26 and 28 are controlled as to 
conductivity, the acidic solution 30 is simultaneously controlled for both 
conductivity and pH. When the conductivity of the solution 30 exceeds the 
control point of the solution 30, for example, 400 micromhos, the 
controller 102 opens the valve 114 to add fresh water to the bath 20, thus 
diluting the solution 30. When the conductivity falls below the control 
point, the valve 114 is closed again. If the conductivity of the solution 
30 exceeds the control point by a predetermined amount, such as 100 
micromhos, the alarm light is activated to notify the operator that the 
flow through valve 115 should be increased. 
The analyzer 110 is a four control point unit, i.e. low-low, low, high and 
high-high. The pH of the solution 30, is maintained within a tight pH 
range to insure that the web 10, after leaving the solution 30, will be 
acidic, yet after air contact and drying will have a neutral pH of 7.0. If 
the dried product has either a higher or a lower pH than neutral, the 
product is unacceptable because degradation of the product fibers occurs. 
In a dye rinse operation, colors fade or streaking or spotting occurs if 
the pH is not closely controlled. 
The pH of the solution 30 is controlled between a predetermined control 
range, for example, 4.5 to 5.0 pH. 
The analyzer 110 provides a direct readout of pH and allows acid to flow 
from the source 120 through the normally open valve 116. If the pH of the 
solution 30 drops to a predetermined low point, e.g., 4.5 pH, the low 
control point relay 135 closes valve 116 to stop acid flow and overrides 
the controller 102, through relay 501, to open valve 114. In this manner, 
the pH of the solution 30 is raised because the supply water from the 
source 34 is of significantly higher pH than the desired pH in the 
solution 30. If the pH of solution 30 falls below the low control point by 
0.3 pH unit, for example, a so-called low-low control point, the analyzer 
110 activates the low-low control relay 132 which activates the alarm 
light 52 and, through the relay 136, activates alarm bell 134. Only the 
alarm bell is deactivated by switch 602 through the time delay relay 136. 
The alarm light 52 is not deactivated by the switch 602. The operator may 
take necessary steps to manually adjust the pH or wait for a predetermined 
time, three minutes for example, for automatic adjustment. The alarm bell 
134 is reactivated by relay 136 if the pH of the solution 30 has not 
increased satisfactorily in the intervening period. Should the pH rise to 
the high control point, for example 5.0 pH, the high control relay 133 
opens the normally closed solenoid valve 116 to allow additional acid to 
be added to the solution 30. Should the pH of solution 30 increase above 
the high control by a predetermined amount, for example, 0.3 pH units, to 
pH 5.3, a so-called high-high control point, the analyzer 110 activates 
alarm bell 134. Only the alarm bell can be deactivated by switch 602 
through the time delay relay 136. The alarm light 52 is not deactivated by 
the switch 602. The operator must take necessary steps including 
increasing the flow through valve 119, a globe valve. The operator can 
then wait for the remainder of the predetermined time, for example, 3 
minutes, for automatic adjustment of this high-high pH condition. After 
the adjustment period, the alarm bell 134 is reactivated if the pH of 
solution 30 has not decreased satisfactorily in the intervening period. 
In dye and finishing operations, the dyes most often used are acid dyes, in 
contrast to the alkaline solutions of a bleaching operation. Therefore, 
the pH analyzer 110 controls the pH by increasing the pH of the solution 
30 rather than lowering the pH. To this end, an alkaline solution is fed 
through valves 116 and 118 to give the final product a neutral or other 
desired pH to eliminate color fade, spotting, streaking or acid attach on 
the product. 
In some operations, temperature is an important factor, in the quality of 
the finished product, whether it be in finishing, dyeing or bleach rinsing 
operations. Control of temperature is directly related to the effective 
removal of solids, (bleaching compound, dyes, mineral salts, etc.) from 
the product. Heat exchangers and live steam injection are used to raise 
the temperature of fresh water, from a mean input temperature of about 
50.degree. F. to the desired control temperature of 120.degree. F. to 
180.degree. F., for example. Manual adjustment by operators by use of 
manual thermometers allows wide fluctuations of temperatures by as much as 
45.degree. F. and often temperatures above 210.degree. F. will be found in 
a typical manual operation. Naturally when this fluctuation occurs, the 
resulting energy waste of boiler fuel, oil and gas is exceedingly large. 
In addition, poorer rinsing characteristics are provided. In the depicted 
embodiment, temperature controllers 180, including thermocouples, control 
temperatures within 3.degree. F. Alternatively, direct readout temperature 
units are used with thermocouples if manual control of temperature is 
desired. Where desirable, temperature recorders may be included. When 
temperatures are controlled in connection with the practice of the present 
invention, better rinsing is maintained at a given temperature, with less 
water waste and fewer solids are carried over from bath to bath. 
Employing a system as described herein, the resulting textile product is 
substantially constant in quality and the rejects are reduced to a very 
low level. Moreover the usage of water, chemical additives and energy were 
reduced to great degree. 
While a preferred embodiment of the method and apparatus of the present 
invention has been illustrated and described herein, it will be understood 
that changes and modifications may be made therein without departing from 
the invention in its broader aspects. The description is intended to limit 
the invention only as set forth in the claims attached hereto.