April 2, 1957
R. w. LUCE
2,787,238
HYGROMETRIC INDICATOR
Filed April 4, 1955
FIG.
70 0 . at’o.
on.
"I’.0. "
FIG. 2
FIG. 6
INVENTOR
I7)
Rghord W. Luce
7'11”,BYM
‘I ‘2) a/éfar/
ATTORN
S
United States Patent 0
1C6
2,787,238
Patented Apr. 2, 1957
2
a compound containing an anhydrous salt, such as
cobaltous chloride, which will change to a hydrate salt
having a diiferent color at a predetermined degree of rela
tive humidity. I propose further to print a'nfadjacent por
‘
‘2,787,233; H
l
_
tion of the paper with an ink, the color or shade of color
of which is the same‘ as the color of the salt compound
either in its anhydrous form or in its hydrated form. i
propose in one form of ‘the invention to print theri-nk
and salt compound on the paper by a half-tone process
10 so that any di?erence between the colors and shades will
be not apparent until after the color break in the salt
HYGROMETRIC INDICATOR
Richard w. timeshares, com. I
Application April 4, 1955, sedans-498517
5 “Claims. (Cl.
has occurred as a result of a humidity change.
A
In still another form of the invention, I propose to
print geometrical ‘line patterns on the indicator paper
This invention relates to hygrornet‘ric indicators, and 15 with a printing ink so that the portion or portions of the
paper containing the salt compound will be completely
surrounded by the printed lines. The remaining portion
more particularly, to hygrometric ‘indicators that may be
used to determine the moisture content ‘of sealed con
tainers and the like.
‘
,
or portions of the indicator paper are then printed in a
,
in shipping or storing such articles as jet'eng‘ine's, ma
color corresponding to the color of the salt compound in
chine tools, or other goodswhich may"ea‘_s‘ily' rust, it is 20 either its anhydrous or hydrated state. When a change
often necessary to determine whether thernoistlirev content
in relative humidity occurs su?icient to change the color
or relative humidity of the packing cases containing the
of the salt compound, a geometric pattern becomes dis
goods is at a level that might‘ caii'se‘rustin'g‘. The use
cernible which preferably had not been previously dis
of color changing hygrometric indicators; to determine the
cernible or rather had been undiscernible prior to the
moisture content in sealed containers“ is" in‘ itself old. 25 break in color ‘caused by the humidity change.
However, the indicators used heretofore have‘ been“ di?i
I‘ propose also to encase‘ the sheet of paper in a tube
in which there is an interior shoulder. The paper is to
be protected on one‘ side (normally its color face) by
because the persons checking the indicators were"not able
a1 sheet of ‘glass which rests on a gasket which in‘ turn
to readily determine whether the indicators showed too 30 bears against the interior shoulder of the tube‘; The
much moisture in the containers or not._ This was be
other side of the paper (normally its rear face) is to be
cause the indicators used- had, no base‘ or‘st'andar'd'colo‘r
. protected by a second tube‘having a ?anged end in con
cult to read, so that many times the goods‘ in the sealed
containers have been severely damaged or even“ ruined
or shade of color to which reference might" be‘ readily
and easily made to determine if the humidity‘ sensitive
indicator had actually changed color.
I,
,
The hygrometric indicators used before havelc‘o'n'sisted
tact‘with the paper. The complete assembly is held to?
gether by havinga portion of the first tube crimped over
35 ‘the ?ange of the second tube so that the complete assem
bly is airtight as‘ is its seal with a container wall when.
of plugs containing a piecelof paper‘on’lwliichiwas con
tained a compound containing" cobaltou's ‘ chloride;
mounted therein.
. Referring, to the drawings,v in. which several embodi;
Cobaltous chloridein its anhydrous salfforr'n'is blue, in
ments of my new type hygrometric indicator are shown,
color, and when it is subje‘cted‘to relative humidity of‘a 40
Fig. 1 shows an enlargement of a piece of indicating
predetermined percent, it'willfcliange'tofa pinki‘col‘orlin‘
paperfon which an anhydrous salt compound and a color
ingtagent are printed by the half-tone process;
Fig, 2 shows‘ an arrangement of colors: and patterns
itshydratedform. This change of color is‘not' striking‘
as the blue and pink colors are ‘of'a dullio'rlpaletdnoso
thatithe change could be‘thou'ght‘of'a‘s‘more iof‘ai‘ch'ah‘ge
on thefindicating paper;
in shading. The result is that when 'a'jcornplete’isheet of 45
paper‘ as used‘ in an old hygornetric ‘indicator is coated
with this mixture, it is hard to determine'éxac'tly when
the “break” occurs, thatlis to‘ say, the ‘exact predetermined‘
hyldroussalt compound printed thereon;
point. of. relative humidity‘ at ' which‘ " thev \cob’altou’s -‘chlo‘-'
ride changes from its anhydrous blue‘s‘tate'to' its‘th‘y'drated
Fig. 3 shows an arrangement of colors opposite that
of Fig. 2 and with a diiferent pattern;
Fig. 4 shows a. geometric arrangement or" printed lines
surrounding portions of indicating paper having an an
50
Fig. 5 shows the indicator of Fig. 4 after the color
pink; state. This isttrue even in indicators‘having’diifen
changeie?ected by a change in‘huinidity; and
ent mixtures of cob‘altous’ chloride‘ whe're‘di?e‘rent-5pjor4
tions of the‘ coated paper will‘lchan‘ge‘afvaifying degrees
constructed?according to my invention.
of relative'humidity.‘ Therefore‘,‘it1‘is asobj , of myth,
vention to provide for a»new‘hygrometric’ihiiicatoriwhe
"
Fig.6 is a side sectional View of a hygrometric indicator
.
. .Theparticular anhydrous‘ salt compound ‘used inmy
which will clearly showthe point ‘at-\which'th "salt‘ibreaks
new typeindicator is not critical. The only require
ment is, that there be a‘de?nite change in color or shade
ata predetermined percent of relative humidity. Com
pounds containingt cobal‘tous chloride are effective as
even to one not ableto recognize colorichan‘ge‘lfotherlth'an‘
there-is afpositive color change‘ of‘ the salt from itsblue
in there is a de?nite contrast of shading and coloring-‘be-‘
tween an. anhydrous salt and‘aY'salt’in"'its‘ihydfated'f‘foi‘m
from aicontrast (light-dark) ip'ointofu'vieWL-t‘
60 anhydrous state to its» pink, hydrated state.‘ Further, the
It is a-further object "of :,,1ny;‘invent_‘ion1‘to?provide?fori
break-point or particular percent of relative humidity at
a new indicator which *may'ibe:easilyrandueconomically‘
produced,
. Breadly .I propose to be: abort-in?ict rLE-Qneéldlats;
which-‘this, change‘ takesqplace ,canheasily be- moved by
modi?cation either-compound‘. Furtherpthe most ef
fectiye ‘ "paper , on. which‘ a to print‘ 4 this i salt a compound» is
(a i ?lter or blotter: typepaper ‘is..~.usually employed’) nvithi? 85 ?lter or» blotting paper.‘
-
' 2,787,288
3
In Fig. l, I show an enlargement of a piece of paper 1
on which is printed at basic color by the half-tone process.
Between the marks of the basic color is also printed by
the half-tone process the letters “NG” which is colored
in the blue anhydrous form of the cobaltous chloride.
The basic background color printed on the paper is made
the same shade of blue or the color of the letters so that
the letters are normally undiscernible.
4
.
When the paper
comes in contact with air of a predetermined moisture
Fig. 4 shows the complete lack of contrast and Fig. 5
the contrasting, readily discernible cross which appears
when the salt breaks as a result of humidity change.
Such inked lines could also be used to separate the basic
color portion and anhydrous portion of the indicator paper
shown in Fig. 3. While an inked outline of the letter
shown in Fig. 2 and of the individual dots of the anhy
drous portion of the half-tone process in Fig. 1 could
be made, it would tend to distract from the contrast be
content or percent of relative humidity, the anhydrous 10 tween the shading when the compound changed to its
salt in the letters will turn to a hydrated form and become
pink in color. This will then indicate to an observer
hydrated form because the indicating geometric pattern
would always be visible at least in outline. In the Fig.
that the moisture content of a sealed container to which
1 construction, however, this might be avoided by ink
the indicator is attached has passed from the safe to the
danger or NG (no good) point at which the contents of a
crate may be damaged. The reading will be clear and dis~
outlining each circle—ink or salt.
Such perimetric con
centration does not, however, present a problem if the
circles or dots of the Fig. 1 construction are small enough.
tinct because there will now be de?nite contrast between
There is shown in Fig. 6 a sectional view of an indicator
the coloring or the shading of the letters and of the color
of the paper. I have found that by printing the base color
plug using an indicator paper which may be printed accord
ing to the forms described above. The plug 10 is adapted
on the paper and the anhydrous form of the salt com- ‘1
pound on the paper in a half-tone process so that the two
to ?t into a sealed container 11 in which it is desired to
know the relative humidity. The plug 10 has a tubu
lar portion 12 which in turn has a shoulder 13 in its in
terior. Indicator paper 14 ?ts in the tube 12 and is pro
tected by a sheet of glass 15. The sheet of glass 15 bears
do not overlap and, in fact, [the unprinted paper separates
the colors, the contrast between the two colors when the
break occurs is more complete. Also when this process
is used, the colors are even more undiscernible before the
break occurs. This is so because any glaze effect between
the contrasting shades and colors is minimized if not
against a gasket 16 which in turn bears against shoulder
13. A second tube 17 is adapted to protect the sheet of
paper 14.
This tube has a ?ange 18 on one end which
bears against the paper on one side and is engaged by the
crimped portion 19 of the tube 12 on the other side. The
Fig. 2 shows a different combination of contrasting
shades of colors and patterns which may be printed on 30 indicator 10 is placed in the side of the container 11 by
avoided completely.
indicator paper to show moisture content in contact with
a hygrometric indicator. Here, a sheet of paper 3 is
being inserted from the inside of ‘the container to the
outside. The indicator is held in place on the side of
printed with a basic color the same shade as the hydrated
the container 11 by crimping a portion of the tube 12 out
form of salt compound with which the letter G is printed.
wards into contact with the container as shown by the
If the compound contains cobaltous chloride as I have used 35 dotted lines. A gasket 20 is placed between the container
and the outside portion of the shoulder 13 so that the
before, this color will be a light pink. It is apparent that
plug is in air-tight relationship with the container. The
if the moisture content of the air in contact with the
tubes 12 and 17 are made of a light metal which may be
paper 3 is above a predetermined level or percent of rela
easily and economically formed.
tive humidity, then the letter G will blend in with the
While I have shown the ?lter paper 14 as being the
background as the salts or" which the letter are printed it)
same as that shown in Figs. 1 through 5, it is obvious
will be in their hydrated state. This will indicate to the
that any type indicator paper could be used which was
observer that the moisture content is above the desirable
printed in any manner. Likewise, it is obvious that the
level. When the moisture content is below the predeter
particular indicator paper shown in Figs. 1 to 5 could be
mined level, salts in the letter G will take on their anhy—
drous form so that, in the case of cobaltous chloride, 45 used in other plug structures than that shown in Fig. 6.
I claim:
they will be light blue in color. The G will then clearly
1. A hygrometric indicator comprising a paper sheet
stand out, indicating to the observer that the moisture
zoned into a ?rst area and a second area, said ?rst area
content of the air being checked is within the safe or G
on said sheet having thereon a compound containing an
(good) ‘level.
Fig. 3 discloses still a further way of combining different 50 anhydrous salt of a given color, said anhydrous salt on
contact with a predetermined amount of moisture chang—
shades of colors on a sheet of indicator paper to given a
ing to a hydrated salt of a different color than that of said
maximum contrast. Here, the sheet of paper 4 may have
salt in its anhydrous form, and said second area on said
a portion 5 printed in a color corresponding to the an
sheet having printed thereon an ink having the same
hydrous form of a salt compound. The upper portion
color as one of the colors of said salt.
6 is printed with a compound of the salt, so that when
2. A hygrometric indicator according to claim 1, where
the paper is subjected to air having a moisture content
in the printed areas of anhydrous salt compound and
above the predetermined level, the contrast between the
colored ink consist of a multiplicity of non-overlapping
colors will be readily apparent.
dots, each colored ink dot being separated from each an
Figs. 4 and 5 show a sheet of indicator paper having
hydrous salt compound dot by an unprinted area of paper.
printed thereon a series of intersecting black lines 7 which
3. A hygrometric indicator comprising a paper sheet
form squares on the paper. A series of squares 8 which
having printed directly upon its surface a shaded area
form a de?nite pattern such as a cross may be printed
and an adjacent area covered with a compound which
with anhydrous salt compound such as used in the other
changes shade at a predetermined relative humidity, the
embodiments of the invention. The remaining squares
9 are then printed a basic color corresponding to the 65 humidity being indicated by the contrast in the two shaded
color of the anhydrous compound. The printed lines are
employed because the anhydrous compound has a ten
dency to concentrate at its perimeter after it has been
areas.
4. A hygrometric indicator comprising a substantially
cylindrical structure which may be inserted as a hermetic
plug in a corresponding hole in a container containing a
printed on the paper and this tends to outline it contrary
to my desire to have the printed sa-lt portions undiscern 70 gas of unknown relative humidity, said cylinder having a
paper sheet part of the surface of which is permanently
ible from the printed ink portions which is necessary if
colored a certain shade and the remainder of the surface
“pure” contrast is to be the indicator as well as color
of which is printed with an anhydrous salt, said salt upon
contrast. It has been found that this can be prevented by
contact with a predetermined amount of: moisture becom
encircling the anhydrous portions by an inked line and
continuing the inked line pattern throughout the sheet. 75 mg hydrated and changing in color, said paper sheet being
.1
2,787,238
exposed to the gas in question through the end of the
cylinder inside the container and exposed to view through
the end of the cylinder outside the container, a glass being
positioned as an air-tight seal between the paper sheet
and the end of the cylinder outside the container.
5. A hygrometric indicator comprising a sheet of paper
that of said salt in its anhydrous form, and the remaining
number of said small areas having printed thereon an ink
having the same color as one of the colors of said salt.
References Cited in the ?le of this patent
UNITED STATES PATENTS
having printed thereon a network of inked lines enclosing
a multiplicity of small areas on the paper, some of said
areas having printed thereon a compound containing an
anhydrous salt of a given color, said anhydrous salt upon 10
contact with a predetermined amount of moisture chang
ing to a hydrated form and having a di?erent color than
1,826,115
Ziebarth ______________ __ Oct. 6, 1931
FOREIGN PATENTS
284,120
752,606
Great Britain ________ __ Jan. 26, 1928
France ______________ ..- July 24, 1933