When we launched The Blast Shop in 1984 choosing which was the best stencil tape to use was a fairly easy decision to make. Anchor in the United States made just three tapes - 111, 112 and 123. 3M, also in the U.S.. sold their own versions of these which, because of the way 3M products were marketed in the UK, were at that time 50% more expensive - so choosing between Anchor and 3M was a no brainer! Finally you had the French manufacturers, Barnier and German brand, Tesa producing paper tapes for shallow blast, hand-cut designs and lettering. Oh! If only it were still that simple...

Fast-forward a few years and then take Anchor as an example. Anchor now manufactured at least a dozen different monumental stencil tapes, some of which are sold in as many as nine different widths! That wasn't the end of it, as the advent of computerised stencil cutting in the late 1980’s meant that new materials, especially PVC, which were previously difficult to cut either by hand or on the old stencil presses, could now be used for stencilling. With this came a whole myriad of new players into the market and the choice of tapes ballooned.

The steady rise in the numbers of masons using PVC based stencil tapes was still massively overshadowed by those using Anchor - Anchor stencil, being readily available, was tried and tested, and was still relatively cheap...So why change..?

Something happened then which caused massive upheaval in the world of stencil tapes and sent a shockwave around the UK memorial trade...South Carolina, the location of  Anchor's stencil factory, was hit by a massive flood, fuelled in part by an offshore hurricane...

Seriously, it was that bad - Thousands of people were displaced, homes and businesses were wrecked and even more tragically, there were some fatalities...
 

Considerations

The basic question to ask yourself is “What exactly do I want to do and how am I going to do it?” Some of the things you will need to consider are …

The material and finish – virtually all tapes will stick well to polished granite but unpolished stone and stone with an open grain such as sandstone will require a high tack tape if stencil filler is to be avoided. Textured and curved surfaces will require the use of a tape that is soft and can be moulded to the shape of the surface.

The depth of blast required and the blasting pressure used – rubber tapes have more blast resistance than PVC based tapes and both will outperform paper tapes.

The detail required – where there is very fine detail and therefore little surface area contact with the stone a thin tape is less likely to lift than a thick tape. You will be able to cut finer detail in a rigid PVC tape than you will in a soft rubber tape which stretches.

The type of backing liner – important if you are not cutting directly on the stone. Mylar or plastic backings resist the knife better than paper backings. Some paper backings delaminate if scored making them a nightmare to remove. Backings have different release properties. Whilst it is generally preferable to have an easy-release liner if it is too easy-release when used on a pinch roller plotter it can lead to disastrous results – the liner separates from the tape and the tape runs off track.

The method of cutting – is the stencil to be cut by hand or on a plotter?

If cutting by hand the tape needs to be easy to cut. This normally eliminates thick PVC tapes from the equation, leaving the choice to be between thin PVC, paper and rubber. Some paper tapes can be put through a photocopier, useful for transferring pre-drawn designs to the stencil.

If cutting on a plotter, what type is it – flat bed, friction feed or sprocket feed? A flat bed plotter will cut any type of tape. If it is friction feed, currently the most popular type of plotter, the tape should be rigid enough to resist the compression forces put on it by the pinch rollers – if it is too soft the tape will not track properly through the plotter. If you are using a sprocket feed plotter, what type of hole configuration does it have? Whilst the industry standard sprocket configuration is ½” some manufacturers have introduced their own variations in the hope of restricting users to their products.

At the end of the day the main decision for many masons will be whether to use a rubber based tape or one of the newer PVC based tapes.

What do we use...

First of all we should confess that we have the best of all worlds – we have a flat bed plotter, a friction feed plotter and a sprocket feed plotter. We can use whichever plotter is the most appropriate for whichever tape we consider to be the best for the particular job we want to do.

For our day-to-day lettering and straight blast design work cut on the plotter we use StoneMask Orange. Because it is a PVC based tape it tracks well on our friction feed plotter. The cut lines on the tape stand out very clearly which make weeding the tape much easier. We can successfully cut letters as small as 8mm. We could go smaller but they are a pain weeding out so we prefer to use a PhotoBlast stencil for these. StoneMask Orange has a strong, clear, silicon-treated PET plastic backing which is recyclable and peels away from the tape easily and because the tape is PVC the stencil does not stretch in the process. The tape itself is transluscent and the stencil can be visually aligned with any existing lettering or ornamentation on the stone before the backing is removed. Again, because the tape is translucent it changes colour where it adheres to the stone and therefore we can clearly see whether there are any potential air pockets which might result in tape lift or centres of letters flying away during the blasting process. We've found that using a sharp, pointed Prikpen to weed the stencil is much better, rather than a knife which we would normally use to weed rubber. Finally, after blasting, StoneMask Orange generally peels away form the stone in one piece, leaving only the centres of letters to be removed with a scraper. All-in-all we think it’s the best all round tape for our day-to-day work and excellent value for money.

If we have to work on either textured or curved surfaces we use Anchor 116 or 155 on our friction or sprocket feed plotters or Anchor 125 - because it is cheaper - on our flat bed plotter. Being rubber tapes they mould relatively easily to the contours of the surface. They have a high tack glue that sticks well to non-polished surfaces. The longer it is left on the stone before blasting the better it sticks – on rough surfaces we leave the stencil on the stone for up to 24 hours before blasting. For better adhesion use stencil filler – but only as a last resort as it can be difficult to remove.

For standard lettering and straight-blast designs hand-cut directly on the stone we use Anchor 125. 125 is a high tack tape with a very easy-release backing. It cuts easily and requires very little pressure – if you use a heat knife it cuts like butter.

When doing shaded designs hand cut directly on the stone we use either yellow PVC lining tape or Barnier 9830. Both tapes are very thin and hold fine detail. The PVC is the better of the two to use but if we already have a line drawing of the design we can transfer it onto Barnier using a photocopier and save ourselves some time. We always use a heat knife for cutting these two tapes.

For deep blasting – 4mm or more – we use Anchor 116 or 155 on our friction or sprocket feed plotters or Anchor 125 on our flat bed plotter. A skilled blast operator should be able to blast to at least ½” deep in granite with these tapes. For even greater depth use two layers – they should give you more than twice the depth.