the invention significantly improves the state of the art in several important ways . firstly , the method is less time consuming and is well suited to complete automation ; secondly , the method employs existing manufacturing tools , thus reducing startup cost ; and lastly , the invention significantly reduces total costs incurred in producing a catalytic converter . this is particularly true in view of the newest emissions regulations that cause converter manufacturers to use less durable substrate materials ( on the order of about 10 % the strength of current converters ). while the invention is particularly suitable and beneficial for use in connection with the newer catalyst substrates , the invention is , of course , equally suited to use with the older substrates . the concept of the invention is the measurement of individual substrates ( or a representative portion of a lot of substrates ) prior to them being wrapped in an intumescent mat . measurement of the substrate is beneficial because individual substrates vary significantly in size . the substrate is generally a ceramic material and the obligatory firing process causes the individual bricks to exhibit different sizes post - firing even though the green state substrates are provided in a generally uniform size . it is highly desirable that the bricks be properly packed , i . e ., fitted or canned . by measuring the catalyst substrate and canning according to that measurement , a designed in pressure on the substrate and mat are achieved . a predetermined annulus , defined by the substrate outside dimensions and the “ can ” inside dimensions , is reliably produced by the method of the invention . by carefully creating the stated annulus during size reduction of the can , the density of the intumescent mat is ensured and the appropriate pressure on the substrate is obtained . referring to fig1 and 2 , the substrate 10 is illustrated as it is being measured preferably by a laser measuring device 12 ( such laser measuring devices being commonly known and commercially available from a variety of sources ). the device 12 may be any measuring device capable of measuring the dimensions of a substrate 10 . in accordance with a preferred embodiment , the laser measuring device 12 employs three lasers 14 positioned with one laser 14 central to the substrate and the two other lasers 14 about 1 / 2 from each end of the substrate , respectively . each laser 14 produces a laser plane 16 that is projected onto ( and past ) the substrate 10 . the light that is received at receptor 18 necessarily includes a gap that corresponds to one of the dimensions of the substrate 10 . since there are preferably three lasers 14 , three measurements are received by receptor 18 . in order to ensure that the measurements are an accurate reflection of the substrate dimension , and because firing is not exact with respect to shrinkage ( the cylinder , for example , might not actually be round ), the substrate 10 is preferably rotated along its own axis and several measurements are taken . an average of all of the measurements is sufficient to employ as a reference for the can reducing procedure discussed hereunder . subsequent to measuring the substrate 10 , an intumescent mat 20 is wrapped around the substrate in one of a number of conventional mat wrapping procedures or new procedures . the wrapping procedure is not critical to functionality of the invention beyond the considerations that must be given to mat wrapping in current canning procedures such as density , uniformity , etc . more specifically , the mat is wrapped around the substrate to form an annular ring of material whose axis is the same as the substrate material . the mat material functions to both mount the substrate and insulate the can from the heat of the substrate . it is very important that the pressure placed on the mat and substrate are the proper amount to successfully hold the substrate , insulate it from shock and substantially fill the desired annulus . because the can 22 is of an oversized dimension initially , the mat wrapped substrate easily fits within can 22 and may be placed therein by hand . the “ loading ” of the can with the mat wrapped substrate is carried out axially since the can is in a perimetrically continuous tubular shape with no break therein ( not a clam shell design which is beneficial because it avoids welding .) the density of the intumescent mat 20 desired is calculated in advance and an appropriate weight mat is employed . the mat may or may not occupy the entirety of the annulus defined by the substrate 10 and the inner dimensions of the un - reduced can 22 . this is immaterial to the invention . because of the control in size reducing the can 22 , the mat 20 will occupy the annulus between the substrate and the reduced can once it has been reduced . the mat 20 will at this point exhibit the density it was designed to exhibit . an optional aspect of the invention , to further ensure that mat 20 will assume the desired density in the size reduced can 22 , is to weigh the mat that will be employed . the weighing of the mat would take place in a weighing device 26 which provides information either to a technician or a controller . by taking into account the weight of the mat 20 as well as the dimensions of substrate 10 , mat density in the size reduced can 22 is virtually assured . typically , mat weights up to 6200 g / m 2 are available commercially in single sheets . while these are generally accurate weights , it is possible for the weights of the mat to be errant . in this case weighing the mat is preferable to ensure proper mat density in the final product . subsequent to loading the un - reduced can 22 , the whole assembly ( substrate , mat and canister ) is placed in a conventionally available size reducing machine 24 , commonly employed in the construction of catalytic converters . as shown in fig6 a machine having 10 - 12 reducer fingers 25 is preferably employed to produce even reduction and uniform stress in can 22 and to thus create a uniform compressive load on the substrate and mat . can 22 is reduced only far enough to result in a structure having inside dimensions that define an annulus of predetermined dimension relative to the actual measured ( or average or representative , where applicable ) outside dimensions of the substrate 10 . this ensures the proper compressive load ( i . e . density of mat 20 and pressure on substrate 10 ) to provide a converter of long life . a secondary benefit of the size reducing procedure is the thickening of the can metal due to the size reduction . this allows the use of thinner ( less expensive ) can metal as the starting material than the specified metal thickness of the end product because at the termination of the procedure , a thinner gauge metal will actually have become thicker so as to meet specifications . the precise change in thickness can be calculated by one of ordinary skill in the art to determine appropriate initial can material thickness . during the canning procedure the converter cross section changes from the view of fig3 to the view of fig4 . the squeezed mat 20 a will be apparent to one of skill in the art . as is also apparent from the illustration of fig4 the reduction in can size is contained in a central area of can 22 and leaves small annular sections 30 at either end of the can 22 . by so leaving these areas 30 , common end cones 32 ( not shown ) are maintained . this , of course , avoids the need for specially formed end cones for each sized can 22 . yet another important benefit of the invention is that it simplifies the construction of dual bed catalytic converters having different mat densities for each brick . as illustrated in fig5 the catalyst bricks 36 , 38 are the same size . the mat however is delineated centrally into two densities . the first is on the left side of the drawing and marked 40 , the second is on the right and marked 42 . the different density of the sections 40 and 42 is occasioned by the different size of the canister , i . e . section 44 and 46 , respectively to sections 40 and 42 . it will be appreciated that section 46 is size reduced further than section 44 to produce a smaller annulus between can 22 and substrate 38 . different densities of intumescent mat provide different properties as known to one of skill in the art . as one of skill in the art will recognize , the procedure described herein may be carried out manually or in a fully automated operation . where a fully automated system is desired and is employed , preferably a controller 28 is connected to the substrate measuring device 12 and the can reducing machine 24 as well as the weighing device 26 ( optional ). a schematic illustration of the system is provided in fig6 . primarily the completed ( i . e ., fired and treated ) substrate is measured with an appropriate measuring device , the device described above being but one example . measurement is preferably carried out to the nearest two or three thousandth of an inch . the annulus desired between the can 22 and the substrate 10 is known because it is dictated by design specification as is the desired density of the mat 20 . following a weighing of mat 20 ( if employed ), the mat is wrapped around substrate 10 in a known manner to provide desired and specified mat characteristics ( i . e . density , etc .) the assembly of the mat 20 and substrate 10 is then loaded into oversized can 22 and the assembly ( 10 and 20 ) and the can 22 are moved to can reducing machine 24 which as stated , is connected to controller 28 . controller 28 communicates the measurements of substrate 10 and the weight of mat 20 ( if weighed ) to can reducing machine 24 . controller 28 further provides specific information to machine 24 regarding , precisely , the degree to which can 22 must be reduced . upon execution by machine 24 of its instructions , a catalytic converter having a can , sized particularly to a specific substrate , is produced and the product is ready for further processing as desired or installation on a vehicle . it will be understood that a person skilled in the art may make modifications to the preferred embodiment shown herein within the scope and intent of the claims . while the present invention has been described as carried out in a specific embodiment thereof , it is not intended to be limited thereby but is intended to cover the invention broadly within the scope and spirit of the claims .