Creating a mask in Corel:

Before making the mask improve the image resolution of your design:

Open

Image > Resample

and insert 635 in the horizontal and 635 in the vertical boxes then click ‘OK’.

Convert your image into a Greyscale file:

The surface of a stamp is either raised or not, the raised parts transfer ink and the recessed parts (floor) do not. In other words it is a binary or 1 bit operation.  All coloured artwork or greyscale artwork involves shading and you need to adjust your artwork to remove the colour, but this has to be done in such a way to maintain as much information as possible about the design, so you don’t lose resolution.  The first step is to convert it to greyscale, click

Image > Convert to Greyscale (8 bit)

The top left hand corner defines the type of file eg (24-bit RGB), after converting it should show (8-bit Greyscale).

Make your artwork the correct size for an A4 sheet:

We make all of our commercial artwork into A4 sized sheets.
You must check that you understand which images the customer intends to be separate stamps and which should be joined together.

To see how large your artwork is at the widest and tallest click:

Image > Crop > Crop to Mask

You will need the design to be this size or smaller:

For an A4    198mm x 285mm
   A5    139mm x 198mm
   A6    95mm x 139mm

You may need to clean up errors at this stage by deleting trash lines etc at the borders.

If the artwork is much smaller you can ask the customer if they want to increase the stamp size to maximise the area of the pack.

If it is larger you will need to either move the designs or shrink one or more of them, again customer approval must be sought before printing negatives.

For a customer who wants a number of individual stamps, you need to get as many designs on one sheet as possible.

If the customer supplies A6 sized artwork these will be replicated 4 times onto one A4 sheet.

If the customer supplies A5 sized artwork these will be replicated 2 times onto one A4 sheet.

To pack the stamps tighter together, cut, paste and move designs using the rectangle shape (or another one of the shapes on the left hand tool bar if more suitable) and then by first clicking outside the design outline the stamp you want to move by clicking CTRL and X, and paste image it by clicking CTRL and V.

To replicate your stamp designs to make up an A4 copy it by clicking CTRL and C, and paste image it by clicking CTRL and V, then fill an A4 sheet up of the same design allowing 6mm separation.

Modifying the artwork to make it suitable for stamp making:
 
You now convert it to Black and White and have the option to make the artwork lines bolder and strengthen the brightness and contrast.

Image > Convert to Black and White (1 bit)

In the pop-up you will now have 7 different ‘Conversion’ options and you can choose any one of these algorithms to convert greyscale colour into either black or white.

For text and line art images:
Use the ‘line art’ conversion option.  Increase the ‘Threshold’ until the drawing looks strong and clear, making the thinnest lines strong enough to hold an inked image.  Check intricate parts of the design by using the left/right click buttons to zoom in/out.

For photographs:
We have found that you get a better result if you resample the design down to 150 dpi before applying the filter.  Open

Image > Resample

and insert 150 in the horizontal and 150 in the vertical boxes then click ‘OK’.
Then apply the filter, we recommend two different conversion options, Jarvis or halftone, you can experiment with what works best for you. With photographs the solid colour is broken up into small pixels.  These must be small enough to retain the important aspects of the design whilst large enough to print up clearly.  The larger the pixels the easier it is to get a printed image.

When using ‘Jarvis’ set the intensity to ‘70’ as a starting point, then experiment from there.

When using ‘Halftone’ adjust the lines per mm, the higher the number the finer the image, but the harder it will be to make a clear stamped image. You can adjust the shape size and the angle of the shape by adjusting the relevant boxes. Use ‘170’ as a starting point.

The artwork is now correct and when printed will be the printed acetate, the negative and the mask can now be made from it.

The artwork you have now created is now the sheet that you will need to print to display your stamps against.

If you are sticking your stamps directly onto your acetate then print it as it is.
If you are printing it so the acetate sticks onto the front of the stamps then you need to reverse it so that the ink is not removed by the adhesion of the stamps, do this by clicking:

Image > Flip > Flip Horizontally

Print this out on clear acetate (called OHP film) using a film and a printer that delivers ink that does rub off easily when scratched.
Consult our printing guide for the best method to print it out so that the black is dark black.

Select all of the image by clicking

CTRL and A

Adjust the paper size to fit the A4 paper size and insert a black border around it by clicking

Image > Paper size
 
Insert the correct paper size dimensions for your design that is:

210mm and 297mm for A4

and click OK

Check whether your design should be in landscape or portrait orientation.
Select Black as the background colour.

Convert the image to a negative by clicking

Image > Transform > Invert

Print it out just as before with the acetate.

Press ‘W’ to utilise the ‘Magic Wand’ tool, the cursor will change from an arrow to a wand.

There is a ‘+’ and ‘-‘ key in the  toolbar above; press ‘-‘ and click on a part of the workspace outside the drawing (the white part).  This turns off the mask overlay.  The drawing should now shimmer and all borders should be highlighted with a dashed line.

If at this stage the outline to the entire page is highlighted you will need to remove this, which you can do by pressing ‘R’ to highlight a rectangle, drawing a rectangle around the entire page and then pressing ‘-‘ to remove the mask.  At any stage if you want to remove part of the mask just highlight ‘-‘ and click on the unwanted mask.

Now create the mask by clicking

Mask > Mask Outline > Expand

A window will open giving you the option to type in how much you would like the mask to be expanded by.  This depends upon the resolution of the image, if the resolution is high then the width will need to be larger. Type ‘40’ as a good starting point.  We like to work with a 6mm (1/2”) separation gap between the stamp images.

At this point you may need to connect separate parts of the mask together. 

You can do this quickest by joining the relevant parts with the rectangle tool on the left hand tool bar.  Alternatively use the ‘Brush Mask Tool’ which is an option on the left hand tool bar or just press ‘B’. You will need to select ‘+’ in the mask mode tool box and left click on one part and drag to the part you want joined to it. Setting the brush to a size of ‘30’ is optimal for 635dpi images.

If you want to reduce the mask in any place press ‘-‘ on the ‘Mask mode’ and point to the place where you need to adjust the mask.

When you have done this you can make the mask look better by clicking ‘Mask’ > ‘Mask outline’ > ‘Smooth’.  This will open a window and you can type a number which you want to smooth the mask by, the higher the number the gentler the curves, first ‘40’ as a suggested radius smoothing.

If you have holes in the mask you can remove them by ‘Mask’ then ‘Mask outline’ then ‘Remove holes’.

Now you have finished your mask and you need to fill in the areas surrounding your masks in black.

Click ‘Ctrl’ & ‘Backspace’ together and a window will open ‘Edit, Fill Transparency’.  Select white as the fill colour and click ‘OK’.  Your mask will now be complete consisting of a black background surrounding white areas that cover all of your designs.

Then print the masking negative (use the same settings as you did for the negative)