Many historical patterns have been resized so that they could be printed in a book or magazine. Others have been resized by yours truly so that they could be put into a scanner. Now if you are used to original size patterns only and are at a loss as to how a garment should be made out of those tiny patterns, read on. But beware: Period patterns are never exact, so if you feel insecure even with a modern Burda or Butterick pattern, you shouldn't try the methods described here. A certain feel for how patterns work is required.
Before you take any of the following steps, you should have printed out the pattern as large as possible. The printout will be referred to as the "small pattern". Do not print the patterns directly from your browser window! Most patterns are much too big for that and don't fit on one page. I didn't want to make them smaller so as not to reduce readability. What you should do is download the image, open it in a graphics software (such as Adobe Photoshop, PaintShop Pro, Micro$oft PhotoEditor, Ulead PhotoImpact etc) and print from there, letting the software fit the image onto the paper page (that's usually a checkbox in the print dialogue). If you don't have a graphics tool, download a freeware or shareware tool e.g. from www.download.com. Make sure it can handle GIF files! A less elegant workaround is to import the image into Winword and resize it until it fits on a page. Be careful to drag only the corner handles! Otherwise you'd distort it.
These come with every part enclosed in a box with measurements marked off along the sides. Typical examples on this site are the early 20th century patterns. These boxes are, in a way, a system of co-ordinates like the ones you know from school, only that the axes are drawn on either side. The points defined by the co-ordinates mark the places of obvious features of the pattern, e.g. corners.
Draw a box of the side lengths given in the small pattern onto paper you don't mind cutting up afterwards, e.g. an old newspaper or a disposable paper tablecloth. If all the numbers along the side get lower towards one corner, that corner will be the zero point. Mark it on your paper. In some patterns there isn't any, but the co-ordinates come with little arrows to indicate which corner they refer to. Now mark off the points indicated by the co-ordinates. (i.e.: If the lower right corner is zero, and you have a 9 up from it, measure 9 cm up from the lower right corner of your pattern and draw a pencil line at right angles to the side into box. And so on.)
Use the shape of the pattern drawn into the box to determine which two of the numbers act together to define a point. When you've marked all the points, connect them to get the outline of the pattern. Don't worry, it doesn't have to be exact - it never was meant to be. Historical patterns require a lot of fitting, anyway.
See illustrations of all above steps side by side.
If you don't feel safe enough drawing free-hand lines between only a few points, divide the side length of the full-size pattern by that of the small pattern and take down the ratio. Select any point on the small pattern, measure its distance from two sides, and multiply the values you get with the ratio. That'll give you a new point you can mark off in your pattern. Do that until you feel you have enough co-ordinates. Don't get it? Here are detailed instructions.
They come without a box, but with measurements. A good example are the 1878-1880 patterns on this site. There's usually two straight lines at right angles - just complete them to form a box, then treat these patterns like box patterns.
The problem is that these patterns often aren't exact in the first place, so calculating co-ordinates between those given (as in the last paragraph of the box pattern instructions above) will likely get you into more trouble than trusting your sense of proportion.
These are the worst you'll ever encounter: Free-form shapes with only the caricature of a yardstick or the statement that it's meant for an xx waist. The late 1890s patterns are an example: Only the sketch of the pattern parts on the fabric, and the fabric width as the only indicator of scale. Or the patterns in Waugh, not quite as bad. But as long as you've got any measurements at all, there's no need to worry. There are two methods you can use: grid, and radial projection.
The grid method is more exact, but you should have a large printout of the small pattern and/or a very sharp pencil for drawing the grid.
We used this at school... You overlay the small pattern with a grid. If your pattern has a little yardstick that tells you that 1/16 inch corresponds to 1 inch in reality, the increments of your grid should of course be 1/16 inch. Or you choose the increments freely, then calculate the ratio between the small pattern and "reality", e.g. between small pattern's waist width and the intended waist width. Just to be sure, calculate the ratio for the breast-waist distance, too.
Now you draw that grid in real-life size onto newspaper. Draw the pattern into the grid by copying one square at a time, e.g. "from slightly above the middle of the left side" of the square to "the lower right corner". See illustrations.
Advanced users may try to distort the proportions of a pattern, e.g. if the breast-waist measurement corresponds with your own but the overall width should be larger. Then your real-life-sized grid would consist of rectangles rather than squares - but make sure that the height-width ratio of the rectangles corresponds with the intended breast-waist/waist-width ratio.
Stick the printout to a corner of your paper. If the pattern has any straight lines, it's a good idea to make it coincide with the edge of the paper. Let's say it's the lower left corner. Calculate the ratio between the measurement given (e.g. fabric width) and its counterpart in the small pattern and take that down. Now draw a straight line from the lower left corner of the small pattern through any outstanding feature, e.g. corners, prolonging them outwards. Now go from line to line, measuring the distance between the lower left corner and the other point of the small pattern where the line crosses and multiply it by the ratio you've got. Mark the distance you get on the line. Lastly, connect the marks in the shape of the pattern. If you feel this is too much free-hand drawing, draw a few more lines through any point of the patten you like and do as outlined above.
If you feel the above instructions weren't enough or hard to understand even though you tried, please contact me and I'll help you and make amends.