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PrecisionMasks FAQs
- What kind of exposure equipment do I need for PrecisionMask film?
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The ideal exposure unit for PrecisionMask film is a Metal Halide light source of between 1 and 2Kw (preferably with a shutter, rather than instant start), at about 30 inches or so distance and with the film held in close contact with the original by a vacuum. We supply a purpose designed unit, see Equipment page. Other sources are www.natgraph.co.uk for Europe and www.mrprint.com/nuarc/ for North America. These types of unit are also commonly used by screen printers - so you may be able to buy a used one, reasonably cheaply and reasonably locally. A Mercury Vapour lamp may be used instead, at a similar distance, but it will be much slower. A fine, dark coloured plastic or rubber foam may alternatively be used to press the film in close contact with the original, instead of a vacuum.
- Can I use my existing exposure unit, which has a UV fluorescent tube (or tubes), to expose PrecisionMask film?
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No, we’re very sorry, but it is simply not possible to achieve fine details or halftones using fluorescent tubes in close proximity to the original. These units give too much undercutting light and, as a result, close up any fine details in the stencil.
- What is the shelf life of PrecisionMask materials?
- The official shelf life of PrecisionMask Stencil Film is 6 months from the date of purchase. If kept in cool dry conditions, this shelf life can often be at least doubled. But if kept on, say, a hot window sill, even in the packet, the heat will accelerate the ageing of the film and can decrease the shelf life and lead to fogging.
The shelf life of undiluted PrecisionMask Water Based Adhesive is also 6 months from the date of purchase. Store in a cool place but protect from frost.
The adhesive may also be stored in its diluted form, but the shelf life may be reduced if it is contaminated in any way during or after dilution.
The shelf life of other components of the PrecisionMask System is , to the state of our current knowledge, unlimited.
- Blotchy patches of stencil film don't wash out.
- Re-soak the film in water for a longer period and then wash out again - the patches will dissolve.
- My PrecisionMask stencil film curls up at the edges when I'm ready to coat it with Carrier Film.
- The film has been dried at too high a temperature - reducing the drying temperature will prevent this from recurring. For those sheets that have already curled, put weights on the edges whilst the wet Carrier Film is drying to prevent the liquid film from pooling. If you are using a PrecisionMask Laminating Machine to coat the Carrier Film, use one of the white plastic protection sheets that are packaged with the Stencil Film to temporarily help you press the curling film flat until the suction of the vacuum bed is holding it.
- I get a headache when I manufacture PrecisionMasks.
- The solvent in the Carrier Film may cause a headache if a high concentration of fumes is allowed to build up in the workplace (see the Safety Data Sheet). Install a suitable extraction system in the coating area and use a purpose built, self extracting PrecisionMask Drying Oven to cure the film.
- Some of the detail stays behind when I peel the PrecisionMasks off the polyester.
- The stencil film was still damp, or it had become damp again by absorbing moisture from the atmosphere, when the Carrier Film was applied OR
- The Carrier Film was not fully cured before attempting to peel.
- My PrecisionMasks are all stuck together.
- Always store PrecisionMasks in a cool, dry place with sheets of paper interleaved between them.
- I can't tell which side up my PrecisionMask should be applied to the glass - both sides look the same.
- In future, make sure a little R is included in every artwork, to indicate the right-reading side of the PrecisionMask. For now, wet the mask for a moment or two in the diluted Adhesive - the mask edges will start to curl away from the side that should be applied to the glass.
- My PrecisionMask curls up at the edges when I try to stick it on the glass.
- In future, make sure that there is a 2mm border of clear Carrier Film around the edge of each mask (i.e. a 2mm black border around each artwork) - the surface tension underneath this border will be sufficient to hold the edges down. For now, press the curling edges down firmly with your finger as the mask starts to dry, until they stay down.
- I can't get my PrecisionMasks to stretch around compound curves.
- Warm the glue and/or the glass slightly, this will make the masks easier to stretch.
- My PrecisionMasks distort when I'm squeegeeing them down.
There are four possible causes of this:
- The Carrier Film was applied too thinly during manufacture. Check the thickness and correct in future.
- The squeegee was dry when squeegeeing the glue from behind the mask and has snagged the surface. Always wet your squeegee with the dilute Adhesive.
- The mask was repositioned but part of it had already stuck down.
- The glue and or glass are too warm - cool them down a little.
- In all cases, if a mask has become a little distorted during application, it can often be rescued by removing it from the glass and laying it upside down for a minute or two to allow it to regain its shape - gentle warming may help.
- Bubbles appear behind the PrecisionMask whilst it is drying.
There are two possible causes of this:
- Bubbles in the glue were not squeegeed out from behind the mask. Be more careful and check the back of the mask through the glass after squeegeeing - if you do spot some at this stage, you can peel the mask off and re-apply it.
- The mask on the glass was dried at too high a temperature and water vapour from the drying adhesive has created bubbles under the mask, rather than permeating out through it. If these bubbles are outside the detail, mask them before blasting. If they are within the detail, wash the mask off and start again. Lowering the drying temperature will prevent this in the future.
- Some of the detail comes away with the Carrier Film when I peel it off the glass.
There are two main causes of this:
- By far the most common problem is the adhesive not being dried properly or for long enough. Many factors can affect the drying time - Carrier Film too thick (check and correct); Too much adhesive left behind the mask (squeegee more carefully and firmly); Ambient temperature too low (warming in an oven at 45 - 48C is ideal); Moist atmosphere (again, warming in an oven at 45 - 48C is ideal).
- Occasionally, the glass surface may be greasy or contaminated with detergent or rinse aid. Wash the glass with an alkali such as Mangers Sugar Soap or a 10% solution of caustic soda. N.B. PrecisionMask Water Based Adhesive does not adhere well to heat treated glasses, such as Pyrex, which have a different surface chemical structure to ordinary glass.
- The stencil film comes completely off the glass when the Carrier Film is peeled.
See the previous answers or, more likely:
- The mask was applied inside out. Re-apply it the right side out (see also the comments in "I can't tell which side up my PrecisionMask etc").
- The mask looks OK, but doesn't engrave.
The holes in the mask are not actually clear. Possible causes:
- Wrong type of exposure unit. PrecisionMask Stencil Film is a high definition product, requiring precise exposure from a point light source. Whilst it can be exposed using a bank of fluorescent UV tubes, this will simply not allow many of the results of which the film is capable - fine lines, halftones and so on. Use a powerful point light source with a metal halide bulb. The PrecisionMask Exposure Unit is ideal.
- Fogged Stencil Film - Stencil film which has been exposed to to bright sunlight, or left in general daylight for a while, or allowed to become very hot, or which is simply old and out of date, becomes partially exposed and thus unusable. Store in the packet until required. N.B. The official shelf life of PrecisionMask Stencil Film is 6 months from the date of purchase. if kept in cool dry conditions, this shelf life can often be at least doubled. But if kept on, say, a hot window sill, even in the packet, the heat will accelerate the ageing of the film and can decrease the shelf life and lead to fogging.
- Translucent black in the artwork master, allowing light to seep through the dark areas, thus partially exposing the film. Use a master with an opaque black image. If using laser film, use a toner density enhancer.
- Stencil Film only partially washed out. Refer to the manufacturing instructions. Soak the stencil film for a few minutes before washing out.
- Over-exposure. If the larger details are engraving straight away, but the smaller details are not engraving at all, over-exposure is the likely cause. Check your exposure settings and, if this still persists, re-check the calibration of your exposure unit.
- My masks are wearing through before I can engrave any depth.
Part 1: The masks are pale blue.
- Unless you are aiming at halftones or equivalently fine detail (in which case you will neither wish to, nor be able to, engrave to any depth), the film has been underexposed. Check your exposure settings and, if this still persists, re-check the calibration of your exposure unit.
Part 2: The masks are bright blue, but they are still wearing through
This will be a combination of one or more of the following factors:
- Grit size. Use 320 grit or finer.
- Grit aggression. Some new grits are extremely sharp to start with. Use a reduced pressure and increased care when operating with brand new grit. We advise recycling grit and regularly mixing a little new in with the old, rather than wearing it out completely and changing the whole lot at once. N.B. Worn grit will actually allow you to achieve a deeper cut. It still shatters the glass almost as well as new grit, but it doesnÕt wear the mask away nearly as quickly. Thus allowing a deeper cut.
- Nozzle size and air pressure. Reduce them both until you get the results that you want.
- I'm getting a speckled or frosted effect around my engraving.
- This indicates sharp new grit at too high a pressure for the mask, particularly with halftone masks. Reduce the pressure until your grit has worn a little.
- I'm getting holes suddenly appearing in the mask when I'm sandblasting.
- This is caused by air bubbles under the mask, which burst when they are blasted. See the section above on avoiding bubbles.
- Little bits of detail fly off when I'm sandblasting.
- The glass surface may have been greasy or contaminated with detergent or rinse aid before the mask was applied. This tends to happen only with certain glasses from certain manufacturers (most can be used straight from the box without problem). It can be avoided by washing the glass beforehand with an alkali soap, such as Mangers Sugar Soap or a 10% solution of caustic soda. N.B. PrecisionMask water based adhesive does not adhere well to heat treated glasses, such as Pyrex, which have a different surface chemical structure to ordinary glass.
- My halftone engravings are stripy or banded.
- This is caused by uneven blasting. Rather than trying to achieve a close, accurate blasting in one or two slow passes along close parallel lines, blast from further away, at a lower than normal pressure, using a multiple series of light passes - thus dusting the surface evenly.
- My halftone engravings are indistinct.
There are four possible causes here:
- Origination. Make sure that you are using the full tonal range for the area of your subject. Be prepared to sacrifice a little tonal range outside the main subject area for the sake of the subject. This can be achieved in Photoshop by the careful use of levels and contrast & brightness.
- Output. You may think that your laser printer is capable of sufficient quality to output halftones. It is not. You will need to use an image setter or process camera to achieve good halftone engravings.
- Exposure. Overexposure is one of the most common problems in engraving halftones. The symptom is the smaller dots failing to engrave. The solution is to reduce the exposure time. Remember, it is not possible to engrave halftones successfully using the wrong type of exposure unit. The PrecisionMask Exposure Unit is ideal.
- Blasting. Halftone engravings are necessarily very shallow. Any attempt to blast depth will preferentially wear away the smaller dots and will also produce tiny sides to the cuts, which will pick up and reflect extra light. Both of which will upset the balance of the halftone image so carefully prepared in the original artwork. Do not attempt to engrave to any depth.
- I'm getting a thin engraved line appearing at the joint of my Continuous PrecisionMasks.
- This is caused by a bubble creeping along the joint as the adhesive dries out, which then bursts as it is engraved. The dabs of Carrier Film at D and E as described in the instructions, help to stop this, as does the zigzag Z in the artwork. If it still appears, despite these precautions (and if it does, it can be seen from the back in reflected light before being blasted), then mask over it.
- My Intaglio engravings are flat, with no 3D effect.
There are four possible causes here:
- Poor artwork. intaglio engraving will succeed, or fail, on the quality of the artwork.
- Incorrect exposure. As described in the instructions, this is a trial and error process, for which there are no set calibrations. Try a number of different exposures (all with the exposure unit well warmed up), see which one works best and then do another, narrower set of exposures, around that until you find the optimum results.
- Too coarse a grit. Intaglio engraving will only work when using fine grit (preferably 400 grade plus, to dust) which has been well worn. The more worn the grit, the better the intaglio results. Use a new or a coarse grit and the mask will wear away far too quickly and the different depths will not be created in the glass. The mask should be seen to wear away gradually as the engraving progresses.
- Under or over polishing after the engraving. We recommend a cork wheel with pumice medium and a light polish, just sufficient to pick out the highlights.
- My engraving somehow looks wrong.
- Always remember that glass is effectively a black
background, upon which your engraving will be white. Engrave the highlights
not the shadows. If the shadows are engraved, the image will be a negative
and simply look wrong. So your artwork should look a bit like a negative -
with black faces, negative halftones and black sails.
None of the above?
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