CA1121764A

CA1121764A - Method of detecting heat seal breaks and package thereof

Info

Publication number: CA1121764A
Application number: CA000295493A
Authority: CA
Inventors: Oliver L. Pouliot; William P. Daly; Robert P. Lewis
Original assignee: Faser Industries
Current assignee: Faser Industries
Priority date: 1977-01-24
Filing date: 1978-01-23
Publication date: 1982-04-13
Also published as: JPS5918253B2; FR2378274A1; FR2378274B3; IT7867123A0; GB1592214A; IT1192323B; JPS5395093A

Abstract

Abstract of the Disclosure Breaks in heat seals between a paper member and a clear plastic member are detected by providing a paper member with a relatively dark coloration, for example dark blue, dark green or dark red, at least in the area of the heat seal, heat sealing the clear plastic member to the paper member in the desired seal. area whereby upon breaking the heat seal there is a distinct color contrast between the break in the heat seal and the relatively dark coloration of the paper and any remaining heat sealed area. The method is especially suited for the manufacture of steril-izable packages or pooches for medical implements. The paper member may have a portion which extends beyond the area to be enclosed by the heat seal when completed. This portion bears indicia, generally printed on the paper, that changes color upon sterilization (either steam or gas sterilization). The indicia herein, portion is adapted to be separated from the package and inserted therein together with any package contents before the heat seal is completed and the package contents are sterilized.

Description

~ ~2~764 1 ¦ BACICGROUND

3 ¦ This invention relates to a method of detecting 4 ¦ breaks in heat seals between paper and plastic, especially 5 ¦ in sterile packages and a packa~e wherein the ~aDer member -`~
6 ¦ is provided with a portion which can be seParated from the 7 ¦ package ~7hich carries indicia that changes color upon 8 ¦ sterilization.
9 ¦ Sterilizable packages or pouches made by margin-10 ¦ ally heat sealing a clear plastic laminate to surgical 11 1 grade kraft paper or the like have come into widespread 12 1 use. The ~aper portion of such packages is designed to be 13 1 sufficiently porous to permit gas or steam sterilization 14 ¦ but is impervious to bacteria. The plastic laminate is heat 15 ¦ sealable to the paper, stable under sterilization conditions, 16 ¦ imvervious to bacteria and permits visual identification of 17 ¦ the package contents.
1~ ¦ Such packages are used for medical implements 19 ¦ that must be sterlle prior to use. The manufacture or 20 ¦ user (such as a hospital or clinic) of such medical im~le-21 ¦ ments is su~plied with a ~ackage heat sealed around three 22 ¦ sides by the packa~e manufacturer. The medical implement 23 ¦ ls then pl.acecl in the package anc.l the Eourth sicle is heat

2~ ¦ sealed to complete the marginal seal between the ~aper and 25 ¦ the plast:ic.
26 Alter sterlli~ation, either by exposure to ethylene 27 oxide gas or by steam autoclaving, by the medical implement 28 manufacturer or by the hospital or clinic, the package and 29 its sterile contents can be stored for indefinite ~eriods of time in a sterile condition.

~7 6 ~

1 To determine if a sealecl package has been subjected 2 to sterilization, it has been cornmon practice to employ

3 indicator inks that change color upon gas or steam sterillza-

4 tion and these indicator inl~s are typically printed on the exterior and/or interior of the paper member oE the 6 sterilizable package.
7 Prior to use, for examPle in an operating room, 3 the inclicator ink is inspected to make sure the package had 9 been properly sterilized and the marginal heat seal o~ the vackage is visually inspected in an effort to detect whether 11 or not the initial heat seal is adequate or whether or not 12 there are any subsequent breaks or ruptures in the heat seal, 13 for example by accldental tampering with -the package after 1~ sterili.zation or by shifting of the package contents in such a way that the heat seal becomes broken or ruptured.
16 Sterilization pouches are conventionall~y made of 17 clear, colorless plastic film heat sealed to white paper.
18 This combination of materials makes it extremely difficult, 19 if not impossihle, to visually determine if the initial 21 seal has subsequently been ruPt~lred or broken by tampering or movement o:E the package contents.
22 To more readily ascertain the validity of the 23 initial heat seal, it has been proposed to lightly tint the 2~ plast-ic laminate member or to coat the paper member with a ~ :ligll~ly L:intecl heat seal. co,~tin~. This approach, however, 26 l~as 17eell far ~rorn satis~actory :in that it is no~ possibl.e 27 to read-LI.y ascertain ~y visual inspection the acle~uacy and 23 completeness oE the ini.tial heat sec11 between the plastic 29 film and the paper member. Moreover, there is no improve-ment as compared to white paper and colorless plastic film 1121~764 1 s regards subsequent breaks or ruptur~s in the he.lt seal¦ :
2 between the p'lastic and the paDer due to tampering with the 3 ~acka~e or movement of the contents of the package. -4 The main difEiculty with indicator inks printed on either side of the paper member is that the package may be 6 subjected to sterilization conditions which are sufficient to 7 cause a color change in the indicator ink 'but insufficient to actually sterllize the package contents. With an Lndicator 9 ink printed on the outside of the paper member the color change will occur as soon as the indicator ink comes in con-11 tact with steam or ethylene oxide gas and long before either 12 gas penetrates the paper member and sterilizes the Dackage 13 contents. Printing the indicator ink on the inside of the 14 paper member is an improvement but again the ethylene oxide gas or steam in passing through the ~aper member comes in 16 contact wlth the indicator ink before reaching the package 17 contents. To cope with these problems manufacturers and 1'8 hospital~ have to follow sterilization procedures with a 19 built-in margin of safety to ensure tha~ the packa~e contents are sterilizecl which means using high sterilization tem~eratures 21 over a sustained period oE time. Because oE these drawbacks 22 the indicator inlcs printed on the ins-ide or the outside of the 23 paDer member s:i~ply'say that the package has been put through 2~ ster:i.'l.:læcltlc)n bnt i~ :is leEt up to the techni.cian to ensure 2~ l:hc-t the correct sL:eriliæclti.on Droeedure has l~ecn observed to 26 e~'ecl:ivc!:ly ster:i.'l.i7.e t:lle pack~ge contcnt~.

29 .

~2~l7~

SUMMARY
The present invention provides a method and a package, especially for sterilization pouches, which over~
comes the problems heretofore encountered in a simple, effective and reliable fashion.
In accordance with one embodiment of the invention, a method of detectin~ a break in a heat seal between a paper member and a clear plastic member comprises providing a paper member dyed a dark color, heat sealing the clear plastic mer~ber directly to the dyed paper member in the desired heat seaL area, thereafter visually examining the heat seal to detect if the previously clear plastic member takes on a translucent appearance in the area of the heat seal which trarlslucent appearance provides a distinct color contrast to detect a break in the heat seaL.
In accordance with a further ernbodiment of the invention, a method of detecting a break in a heat seal between a paper mernber and a clear plastic member in a sterilizable package comirises providing a paper member dyed a dark color which is sufficiently porous to permit gas or steam sterilization but is impervious to bacteria, heat sealing the clear plastic mernber directly to the dyed paper member in the desired heat seal area, there-after visually examin:i.ny the heat seal to detect i~ the previously clear plastic mernber takes on a translucent appearance ir- the area of the heat seal which translucent appearance provides a distinct color contrast to detect a break in the heat seal.
~he invention also provides a package which is especially useful as a sterilization pouch wherein breaks or ruptures in the heat seal due to either tampering with ..

7~i4 the package of movernent of the package contents can be readily detected visually by the user of the package con-tents just prior to use.
In accordance with this aspect of the invention, a package comprises a clear plastic member heat sealed directly to a paper member dyed a dark color such that upon breaking the heat seal the previously clear plastic member takes on a translucent appearance in the area o~ the broken seal which provides a distinct color contrast between the break in the heat seal and the dark color of the paper in any remainingheat sealed area.
The package may also include a member having the desired indicator ink printed thereon which is inserted into the package together with thelimplement to be steriliæed prior to completing the marginal heat seal and subjecting the package to sterilization. The indicia bearing member is provided by printing the indicator inks on a portion of the paper member of the package which extends beyond the area enclosed by the marginal heat seal and making it readily separable from the package. The indicia bearing portion - 5a -L217~;4 1 ¦ inserted wi~h ~he item or imPlement to be sterilizecl in the 2 ¦ package, can be r?ositioned and oriented such that the 3 ¦ indicator ink Eaces the plastic member of the paclcage which 4 ¦ means that the sterilization gas will act on the indicator

5 ¦ ink to cause tlle color change at the same time or after

6 ¦ sterilization of the package contents has been accomplished.

7 This provicles a much better indication to the ultimate user

8 ¦ of the sterile item that it is, in Eact, in a ste~ile

9 ¦ conclition and not simply that the package has gone through a

10 ¦ sterilization procedure.

11 ¦ The method may also include providing a paper

12 1 member wherein the paper member has a portion extending beyond

13 ¦ the area to be enclosed by the heat seal when completed, said 1~ ¦ portion bearing indicia that changes color u~on sterilization, inserting the item or implement to be sterilized into the 16 ¦ open-ended Package, separating the indicia bearing portion 17 ¦ from the package and inserting said separating portion into 18 ¦ the package with the indicia visible through the plastic 19 ¦ member, heat sealing the open end of the package and subject-20 ¦ ing the sealed package to sterilization. Preferably the 21 ¦ indicia bearing portion is positioned between the item to be 22 ¦ sterili.zed and the plastic member with the indicia visible 23 1 throup,ll the plastic mernber. This, oE co-trse, (lepends on the 2~ ¦ nature and the .size o~ the i.tem or implement to be sterillzed.

26 ¦ n~SCRIPTION 0~ I'IIE DRAWI~GS
27 ~ _ _ ~ __ _ _ _ ___ _ __ 8 1 The present invention will be more fully understood 29 ¦ :Erom the following descri~tion taken in conjunction with the 30 ¦ accompanying dra~ings wherein:

~ ~ ~2~76~

1 ¦ ~ig. 1 is a top plan view partly broken away of 2 ¦ a sterilization paclcage or pouch accorcling to the invention 3 1 marginally heat sealecl around three sides of the package 4 ¦ and shaded to indicate that the paper member is dark blue;
5 1 Fi.g. 2 is a top plan view of the sterilization 6 ¦ pouch shown in Fig. 1 heat sealed marginally along the 7 1 fourth side o:~ the package to enclose the package contents 8 ¦ which, i.n this instance, is a pair of scissors;
~ig. 3 is a sectional view taken along line 3-3 10 of Fig. l;
11 ~i~. 4 is a sectional view partly broken away 12 taken along line 4-~ of Fig. 2;
13 Fig 5 is a top plan view partly broken away of

14 a sterilization pouch according to the invention illustrating various ways in which breaks or ruptures in a heat seal can 16 occur;
17 Fi.g. 6 is a bottom plan view of a sterilizable 18 pouch according to the invention from the pal?er side and 19 having triangular tear-ofE indicator T)ortion~s;
l~ig. 7 is a top plan view of the sterilization 2]. pouch of Fi~. 1 from the plastic side showi.ng the marginal 22 heat seal completed and one of the tri.angular shaped indicia 23 bearing portions separated from the package and inserted into 24 the paclcag~e :i.nterior with the package contents with the indicia visible thrc)ll~h ttle plastic mernber.
26 l~:ig. 8 i.s a top Dl.an v:iew p.lrt:ly broken awa,v o~ an 27 alternate ernbocli.ment ol~ the present :inventlon o~ a steriliza-28 t:iOIl l?ouch :Erom the plastic side; ancl 29 Fi.g 9 is a top plan view, partly brolcen away, of a further embodiment o~ a sterilization pouch of the invention also .Erom the pl.astic side thereoE.

~ 176~

1 ¦ UESC~IPTION

3 ¦ The preferred embodiment o:E a sterilization pouch 4 ¦ shown in Fig. I and 2 of the drawin~ is shown to include a 5 ¦ paper member l0 having a dark coloration (in this illustra-6 ¦ tion, dark blue) and a clear plastic laminate 12 which is 7 ¦ marginally heat sealed around three sides of the package in ¦ Fig. 1 and around the fourth side of the packa~e in Fig. 2 9 ¦ to complel:e the marginal heat seal 1~'~. The chevron con-10 ¦ :Eiguration at the top of the package is used to facilitate 11 ¦ manual openin~ or peeling apart of the package to gain access 12 ¦ to the package contents which is .shown in Fi~. 2, for illus-13 ¦ trative purposes, as a pair oE scissors 16.
14 ¦ The paper member 1~ can be conveniently dyed or

15 ¦ tinted the desired relatively dark color, for example dark

16 ¦ bluel dark green, dark red, dark brown, dark grey, or black.

17 ¦ Instead of dyeing or tinting the paper member 10, the paper

18 ¦ member can have a relatively dark coating applied thereto,

19 ¦ at least in the heat seal area. This can readily be accom-

20 ¦ plished by overprinting all or only the seal area of the

21 ¦ paper member 10 with a dark ink such as the dark colors

22 ¦ enumerated previously. The dye, tint or ink should be

23 1 selected so as to be stable under sterilization condi.tions.
2~ ¦ Readi.ly available surgical ~,rade IcraEt paper 25 ¦ tlclVing the cles:ired po-rosity char,tcteristics can he reaclily 2~ ¦ (Iyerl or overpr:inl~e~] to provide the desirecl relatively dark 27 ¦ coloratlotl Eor tlle p,lper member 10.
2~ ¦ 'l`he term "paper" as used herein also a~pl;.es to 29 synthetic or artificial paper materi,als made from plastic ~ibers and the like, as well as conventional paper products 1~21764 l ~ havi the necessary characteris~ic 5 for use in ~terilization 2 pouches. ~n example of synthetic paper is a spun boncded 3 polyelllyl.ene sold hy DuPont uncler the traclemark "TYVEK".
4 The l?lastic member 12 is ~referably a laminate o.E a polyester, such as pol.yethylene terePhthalate sold 6 under the trademarlc "MYL~R", and a heat sealable thermo-7 plastic materiaL such as polyethylene, polypropylene, ethylene vinyl acetate, an ionomer such as ~uPont's "SURLYN", co-9 polyme-rs and mixtures of the Eoregoing. The polyester layer forms the exterior of the package and the heat sealable 11 thermoplastic material inter~aces with the paper member 10 :
12 and forms the marginal heat seal 14.
13 ¦ Heat sealing the plastic member 12 to the paper 14 member 10 around the margin of the t~ackage as sho~m in Figs. 1 and 2 of the drawing can be accomDlished using 16 conventional heat sealing equipment and techniques. Generally, 17 the heat seal is made wide:enough to guarantee an adequate and 18 complete seal around the margin of the package initially 19 formed with a heat seal around the three sides wi.th the fourth side comple~ed after the package contents are insertecl therein 21 as shown in Fig. 2. If desired, a number oE t~arallel spaced 22 apart seals can be effected in the area of the marginal heat 23 seal 14. This is co~nonly known in the indu.stry as a rih seal 2~ and is employecl to .imparl: acldi.tional. ~eel. strength to the heat seal beLweell the pllstic member 12 and the paT~er member 10.
26 ~ccorcl:in~ to the invention, the pl.. lstic member 1227 c".~tlibil:s a re:Lcltive:Ly translucellt a~pear.].rlce wll:ich can be 28 clescribed as cloudy or milky as compared to the clear member 29 itse:LE, upon rupture or breaking of the heat seal area 14.
This cloudy or mill<y appearance is believed to result Erom z~

1 e he.lt sealin~/ operation and only comes into being when 2 the heat seal is ruptured or broken. This phenomenon is 3 believed to result from a surface con:Eormation by the plastic 4 member l2 ~o ~-he surface of the paper mem~er 10. The paper mc?ml~c?r 10 ustlally has a dull or matte fini.sh and this is 6 duplicatecl in the seal area of the film in a cloucly or milky 7 appearance upon rupture or breaking of the heat seal 14.
Fig. 5 o:E the dra~7ing ls intended to illustrate 9 how the present invention provides a visuaL contrast ~or readily detecting breaks or ruptures in the hea~ seal between 11 the paper member ln and the plastic member 12, whether due to 12 part-ial opening of the package, either intentionally or 13 unintentionally, or b~ shiEting of the packa~e contents. In 14 Fig. 5 the plastic member 12 is shown ~ulled back and separated from the chevron portion o the heat seal area 14. The left 16 side of the f-igure shows the cloudy or milky appearance 18 17 from the heat seal side of the plastic member 12, whereas the 18 right side of the figure shows the contrast that results from 19 the exterior side of the Plastic film 12. Note especially the marked contrast of the broken hea~ seal area 18 with 21 respect to the dark coloration oE the paper member 10 itself 22 ancl the remainin~ sealed area 14. It should also be noted 23 t~hat the sealed area 14 has a glossy, clear a~pearance which

24 :Ls in contras~ to ~:he dul.:l or matte Einish appearance oE
tlle l~nper mc?mber l() t:hrough thc? p:Lnsl.i.c membc?r 12 outsicle of 26 thc~ se<l:l. area 1~l. 'rhis contrasl: can be use~cl to cletect voicls 27 or delr~(?cts i.n the herlt seals rrlclde l~y th~! packclp,e manuEacturer 28 and also the paclcager.
29 ~lso illustrated in Fi~. 5 is the visual contrast that results when the package contents sllcll as the pointed llZ17fi~
. ~ , 1 end oE scissors 16 shifts and DierCeS or ruptures the heat 2 seal l~. As can be seen, this results in a readily discernible 3 translucent apPearance 18 which i.s in dist:inct color contrast 4 with the dark coloration oE the paper member 10 through the plastic member 12 in the unsealed areas of the package and 6 is also in distinct color con~rast with the remaining heat 7 sealed area 14 which shows the coloratlon of the paper member 10 in a clear and glossy fashion. Thus, in the case o~ a dark .
9 blue paper member 10, the user of a sterilized package such as showll in ~ig. 2 can readily determine by a simple visual ll examination if the packa~,e, after sterilization, has been .
12 opened, either intentionall.y or unintentionally, that ls, by 13 pee].lng apart the two member 10 and ].2 or whether the package 14 contents, such as the sclssors 16 has shifted and ~ierced or ruptured the heat seal 14. In either instance, the trans-16 lucent portion 18 which has a cloudly or milky appearance 17 is in distinct color contrast with the dark coloration o~ the 18 paper member 10 itself, which in this case is dark blue, and 19 the remairl-ing heat sealed area which has a clear, dark blue coLoration, but is glossy in appearance as compared to the 21 matte or dull finisil of the paper member 10 itselE outside 22 the seal area.
23 '!'he same, highly visual color contrast results from 2~ llnpart:ing l:o tlle paper mc!ml.)er 10 a rc-~lat:ivelY clark coloration .s~.lcll as dnrlc bl.l.le., (.larlc precll, darlc recl, clarlc brown, darlc 26 f~rey, or bLa.ck.
27 l~eEerr:i.ng now to :Fif~9. ~ and 7 Ihe trianf~ular shaped 28 portions 20 extendin~.T beyond the inver~.ed V-end seal which is 29 beyond the area to be enclosed by the marginal heat seal 14 when comp]eted (F:ig. 7). As shown in ~ . 6, the paper 10 ~ ~Z~ 4 1 ¦ may have a white area or block printed thereon so th~t 2 ¦ portions 20 can bear lndieia that changes eolor upon 3 ¦ steriliæation, one portion bearing indicia that changes 4 ¦ color upon steam sterilization ancl the other norti.on 20 5 ¦ indicia that changes color upon gas steriliY.ation such as 6 ¦ ethylene oxi.de gas. The indlcia whieh is commonly referred 7 ¦ to as indicator inks is ~enerally shown by the reference 8 ¦ numeral 22.
9 ¦ - Suitable indicator inks .for the indicia 22 are 10 ¦ any of the commercially available and commonly used indicator 11 inks for sterilization ~ouches. A typical indicator ink for 12 use with steam autoclaving is a chemically active ink that 13 changes from pink to dark brown during steam au~oclaving.
14 A typical indicator ink for use with ethylene oxide sterilization is a chemically active ink that changes color 16 from light brown or tan to orange upon exposure to ethylene 17 oxide gas sterilization.
18 Steam autoclaving and ethylene oxide ~as are known 19 sterilizati,on techniques ancl the present inventi.on is well adapted to these procedures.
21 An item to be sterilized such as the scissors 16 22 shown in Fi~. 7 is i.nserted through the open end of the pouch 23 shown in ~`ig. 6. Depending on the steri:lization procedure 2~ to be emr~loye(L, the technician separates the proper inclieia bearing port:ion 20 each oE wh:ieh i.s attachecl to the paper 2G por~i.oll 'L0 a~- 25 and ~reellt: thereb~tween a~Long line 2~. The 27 technician or operator then lnserts the separated ~ortion 20 28 into the paclcage with ~he indicia 22 vlsible through the 29 ~lasti.c mernber 1.2 as shown in Fig. 7. The marginal heat seal 14 is then completed and the paclcage is ready for sterill~.ation.

Z~7~;4 1 During sterilization, the sterilizinp, medium, steam 2 I or ethylene oxicle ~,as, sterilizes the scissors 16 and at the 3 I s~me time or afterwards, reaches the indici.a 22 which then 4 undcrfroes the ;.nd:icated color chanc~,e to indicate ~hat the packct~,e contents and not just the paclcage itself are sterile.
6 Depencling on the nature and size of the item or imp].ement to 7 be ster11ized, it is preferred to ~osi.tion the portion 20 8 ~ which is in~serted into the pouch between the item to be 9 I sterilized anti the p1astic member which ensures that the 10 ¦ sterilizatioTI meclium will not cause a color chancs,e in the Il ¦ color sensit-ive indicia until after the sterilizing medium 12 ¦ has cont.actecl the item to be steri.lizecl. In any event, the 13 ¦ indicicl 20 must be v;.sible through the Plastic member 12 when 14 ¦ the porl:i.on 20 is separated ~Erom the packacs,e and inserted into ¦ the ilILerior thereof with the item to be sterilized.
16 ¦ The preferred embodiment shown in ~igs. 6 and 7 has 17 I a ~urther advantage in that sealed ~aclcages ready for 18 ¦ sterilization can be se~regated by t:he intended sterilization 19 ¦ proceclure to be emt~loyed l)y virtue of the Eact that one of ¦ the incliclcl-be~rin~, portions 30 is missin~ from either the 21 ¦ left or rl~.~,ht sicle of each ~sealed pouch when t:he po~lches are 22 I J.ined U!) and o-ri.ente(l l.n l,l~e s~ e cl-i.rccl,.ioll. TI1~JS~ :it :i.s easy 23 ¦ Lo delect :if a paclc~ ,e (les:i~rn.lte(] -Enr ~ste.:lm ste-ril:ization has 2~i ¦ beconle nli.xecI ln w;.th paclca~,es cIesi~nated for etllylene oxide

25 ¦ s~eri.lizat:LolI.
2G ~ l~ .s .~ an(:l 9 show alternate embo(I-i.ments of the 27 ¦ presetlt inveI-lt:ion. In ]i.~ , the indi.cict beari.n~ Porti.ons 20 28 1 are clef:ine(I vi.a perforate(I line~s 2~ at the bottom or open end 29 ¦ of the sterilization Pouch. A:Eter the item to be sterilized 30 ¦ is inserted into the pouch under plastic member 12, the ~ --i3-~ 6~a ~
.
l ¦ clesirecl portion 20 of the paper member 10 is separated and 2 ¦ inserted into the poucll with the item to be steri.lized with 3 ¦ the indicia 22 visible throug} the plastic member 12. The 4 ¦ transverse heat seal across the bottom shown by dash lines 5 ¦ is then macle to complete the marginal heat seal 14.
6 ¦ The embodiment shown in Fig. 9 is similar to the 7 ¦ embodiment shown in Fig. 6 except the end seal opposite thè
¦ open end of the pouch is a straight transverse seal and the ' 9 1 ,portion of the paper member 10 extending beyond the area to lO ¦ be enclosed by tlle marginal heat seal 14 is divided into two ll ¦ rectangular indicia beari.ng portions 20 via perforated llne 24.
12 1 The steriliæation pouch of the invention will 13 ¦ typlcally bear other indicia as shown in Fip,. 6, for example 14 ¦ on the exterior side of the paper member 12, nreferably in a 15 ¦ whitened area, to designate for exam~le the package contents, 16 ¦ the sterilization date, the expiration date and the like.
7 1 The color sensitive indicia 22 is commonly printed 19 o the paDer member 0 using known techniques.

22 ;

26

27

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. Method of detecting a break in a heat seal between a paper member and a clear plastic member which comprises providing a paper member dyed a dark color, heat sealing the clear plastic member directly to the dyed paper member in the desired heat seal area, thereafter visually examining the heat seal to detect if the previously clear plastic member takes on a translucent appearance in the area of the heat seal which translucent appearance provides a distinct color contrast to detect a break in the heat seal.

2, Method of detecting a break in a heat seal between a paper member and a clear plastic member in a sterilizable package which comprises providing a paper member dyed a dark color which is sufficiently porous to permit gas or steam sterilization but is impervious to bacteria, heat sealing the clear plastic member directly to the dyed paper member in the desired heat seal area, thereafter visually examining the heat seal to detect if the previously clear plastic member takes on a translucent appearance in the area of the heat seal which translucent appearance provides a distinct color contrast to detect a break in the heat seal.

3. Method of claims 1 or 2 wherein the paper member is surgical grade kraft paper.

4. Method of claims 1 or 2 wherein the plastic member is a laminate of a polyester and a heat sealable thermo-plastic material.

5. Method according to claim 1 wherein the paper member has a portion extending beyond the area to be enclosed by the heat seal when completed, said portion bearing indicia that changes color upon sterilization, inserting the item to be sterilized into the package before it is completely sealed, separating the indicia bearing portion from the package and inserting said separated portion into the package with the indicia visible through the plastic member, completely heat sealing the package and subjecting the sealed package to sterilization.

6. Method according to claim 2 wherein the paper member has a portion extending beyond the area to be enclosed by the heat seal when completed, said portion bearing indicia that changes color upon sterilization, inserting the item to be sterilized into the package before it is completely sealed, separating the indicia bearing portion from the package and inserting said separated portion into the package with the indicia visible through the plastic member, completely heat sealing the package and subjecting the sealed package to sterilization.

7. Method of claims 5 or 6 wherein the indicia bearing portion is positioned between the item to be steri-lized and the plastic member with the indicia visible through the plastic member.

8. Package comprising a clear plastic member heat sealed directly to a paper member dyed a dark color such that upon breaking the heat seal the previously clear plastic member takes on a translucent appearance in the area of the broken seal which provides a distinct color contrast between the break in the heat seal and the dark color of the paper in any remaining heat sealed area.

9. Sterilizable package comprising a clear plastic laminate of a polyester and a heat sealable thermoplastic marginally heat sealed to surgical grade kraft paper dyed a dark color which is sufficiently porous to permit gas or steam sterilization but is impervious to bacteria such that upon breaking the heat seal the previously clear plastic member takes on a translucent appearance in the area of the broken seal which provides a distinct color contrast between the break in the heat seal and the dark color of the paper and any remaining heat sealed area.

10. Sterilizable package comprising a clear plastic member heat sealed directly to a paper member which is suffi-ciently porous to permit gas or steam sterilization but is impervious to bacteria, said paper member being dyed a dark color such that upon breaking the heat seal the previously clear plastic member takes on a translucent appearance in the area of the broken seal which provides a distinct color contrast between the break in the heat seal and the dark color of the paper in any remaining heat sealed area.

11. Sterilizable package of claim 10 wherein the paper member is surgical grade kraft paper.

12. Sterilizable package of claim 11 wherein the plastic member is a laminate of a polyester and a heat sealable thermoplastic material.

13. Sterilizable package according to claim 10, wherein the plastic member marginally heat sealed around three sides to a first portion of the paper member so as to leave an opening at one end for inserting the package contents, said paper member having a second portion extending beyond the area to be enclosed by the marginal heat seal when completed, said second portion bearing indicia that changes color upon sterilization and means releasbly joining said first and second portions for separating said second portion from said first portion for insertion together with the package contents into the package prior to completing the marginal heat seal and sterilization of the package contents to indicate that the package contents have been subjected to sterilization.

14. Package of claim 13, wherein said second portion extending beyond the area to be enclosed by the heat seal has two parts, one part bearing indicia that changes color upon steam sterilization and the other part bearing indicia that changes color upon gas sterilization and wherein the releasable joining means includes means enabling the indi-vidual separation of each part from the package, to signify on its face to a user that the package is to be subjected to steam sterilization if the one part is removed and to gas sterilization if the other part is removed.

15. Package of claim 13, wherein the marginal heat seal includes an inverted end V-seal joining two side seals and the indicia bearing portion of the paper member extend-ing beyond the inverted V-seal is at least one triangular shaped member.

16. Package of claim 15, wherein two triangular members are provided, one member bearing indicia that changes color upon steam sterilization and the other member indicia that changes color upon gas sterilization and wherein the releas-able joining means includes means enabling individual separation of each triangular member from the package to signify on its face to a user that the package is to be subjected to steam sterilization if the one member is re-moved and to gas sterilization if the other member is removed.

17. Package of claim 13, wherein the releasable joining means comprises a partially precut or perforated line in the paper member.

18. Package of claim 13, wherein the paper member is surgical grade kraft paper.

19. Package of claim 13, wherein the plastic member is a laminate of a polyester and a heat sealable thermoplastic material.