Suppliers of the finest quality Photo Resist and Sand Blasting Equipment

10/254 Milperra Road, Milperra NSW Australia 2214

Phone: (61) 02 9772 1999   Fax: (61) 02 9792 2374 

Email: sales@problast.com.au

 

PROCEDURE DOCUMENT

 

 

SANDBLASTING  PHOTO IMAGES

USING COREL PHOTO-PAINT 9 or 12

 

These notes will take you through the process of preparing a photograph for sandblasting. This procedure is based on Corel Photo-Paint 9 and 12, however the concepts covered in these notes should apply to most other software packages. These notes are intended as a guide only and will require your own experimentation to get the effect you need.

 

Note: these procedures cannot be applied to versions of Photo-Paint prior to Version 9 as they did not contain suitable Halftone tools.

 

SCANNING AND IMAGE SIZE

Before starting we need to consider one important rule. “The bigger, the better!” This rule applies to both the original photo that you’re working from, and the size of the final sandblasted image.

 

First step is to scan the image, you should set the scanner to B&W photo or Grayscale as we’re not concerned with colours. The scan resolution will depend on the size of the original photo. Typically:

·         If the original photo is about the same size as what you want to sandblast you can scan with a resolution of 150 – 300 dpi.

·         If the original photo is considerably smaller and will need to be stretched to cover the piece you want to sandblast, you’ll want to scan at 300 - 600dpi.

 

Scanning at resolutions that are higher than necessary will only create larger files for your computer to work with which may slow your computer and use more disk space without making any difference to the final sandblasted image.

 

You might need to change the contrast and brightness to bring out the detail in the photo, this can be done in either your scanner settings or when you open the file in Corel Photo-Paint.

 

After you open the image in Photo-Paint you should set the physical size of our output image, this is the actual size that you want your sandblasted image to be.

 

 

This is done with  Image > Resample, then set the Image Size to the physical size that you require.

Resolution should be set to 150 –300 dpi.

 

 

 

TOUCHING UP THE IMAGE

In most cases you’ll want to remove any distracting background from the photo to just leave your subject. There are many ways to do this in Photo-Paint, and after a while you’ll develop your own approach.

You can do this with the Freehand Mask tool  or with the Magic Wand Mask Tool.  Select most of the background, then delete it. Now use the Paint Bucket to fill the background black.

 

At this stage, depending on the image, you might find you have a very distinct edge on your subject.

Select the Paint Tool,  and select a nib with a soft edge. , also make sure your paint colour is set to black. Now go over the sharp edge left by the lasso tool and soften it.

 

         

 

Now take a good hard look at your image, are there any dark black areas (e.g. shadows), or bright white areas (e.g. teeth) within your image? These will sandblast as solid areas in your image and look unnatural. What you need to do is select any extremely bright areas and just slightly darken them to a light grey. You also need to select any black areas and slightly lighten them to a dark grey.

 

CONVERT TO HALFTONE

The next step is to convert our photo to a halftone screen. This process will convert your photo to a series of fine dots just like the photos you see in a newspaper.

 

Photo-Paint 9:     This is done with Image > Mode > Black and White (1 Bit).

Photo-Paint 12:  This is done with Image >Color Mode > Black and White (1 Bit).

 

 

Set the conversion type to Halftone, and the Screen Type to Round. The lines per inch setting will determine how fine the detail is in your image and will range from 20 to 40 lines/inch depending on the material you want to sandblast. The larger the lines per inch, the more detail the final image will contain, however it will also be harder to wash out the resist and sandblast! For  stone or metal set the lines per inch to 25 lines per inch, 30 degrees, for glass set the lines per inch to 35, 30 degrees. If interference patterns start to appear amongst the dots try changing the angle of the dots.

 

If you are etching glass, you might like to experiment with setting the conversion type to Jarvis, leave the Intensity setting at 100. The Jarvis conversion will often give you a more detailed image.

 

At this stage it often helps to print the artwork on plain paper and review it for any solid areas that are too dark or light, you may need go back a few steps to touch up just those sections of the image.


CREATE A NEGATIVE

There’s one more step to go, the artwork needs to be inverted to become a negative. The reason for this is that anything black in the artwork will become sandblasted area (white frosted on glass), so imagine someone in your original photo with black hair will end up sandblasted with white hair!

 

 

To convert the image to a negative , Image > Transform > Invert.

 

There may be times when you don’t want to change your image to a negative, for instance you may wish to paint fill your etching with a dark colour.

 

PRINTING

It is crucial that you produce a good print for exposure. While Vellum will provide acceptable results for coarser images, the best results for high detailed work will always be achieved by using Laser Film or Inkjet Film.

 

EXPOSURE AND WASHOUT OF FILM

Your artwork consists of thousands of tiny dots and you must be careful not to over expose your resist. Overexposure can cause undercutting (i.e. light seeping in around and under the black), which can then result in difficuly in washing out the resist and a loss of image detail.

 

A proper washout technique is required to achieve a good resist. Washouts should be done as quickly and evenly as possible so as not to saturate the resist and wash away the tiny dots. Keep perpendicular to the resist with the water spray at about 15 centimetres away.

 

It’s not hard to washout photographic images, but you will need to practice the correct washout procedure.

 

DRYING THE RESIST

Drying is the same procedure as doing any other sand blasting job. Just be gentle with the blotting towel while the resist is still wet.

 

APPLYING THE ADHESIVE – SR2000 Resist

It is vital that you use a very thin layer of adhesive so that blasting produces the etched image fast. We recommend the spray on adhesive method of applying adhesive directly to the resist using either thinned down RZ-2 adhesive in our adhesive spray gun or using the spray can adhesive method. Either way a very light, even coating of adhesive is required.

 

Using the sponge brush method onto the product to be blasted may work but it is difficult to apply a very thin, even layer of adhesive this way and you most probably won’t get 100% success.

 

Apply the resist to the product to be blasted in the usual way.

 

ETCHING

We recommend an air pressure setting of 20-25psi when using a pressure pot system. Low pressure will reduce the risk of blowing off the tiny half tone dots.

 

Again you need to strictly follow sand blasting procedures holding the nozzle 15 centimetres away from the surface at a 90o angle. Not keeping your nozzle perpendicular to the surface can cause cutting under the resist dots.