How to Give a Wall Clock Luminous Hands and Time Interval Markers




Posted in TechnologyClocks

Introduction: How to Give a Wall Clock Luminous Hands and Time Interval Markers

About: I am a retired analytical chemist living with my wife Cynthia in Cornwall, south west England. I have held the UK radio amateur call sign G3PPT since 1961. I have been interested in computing since the day...

We wanted a bedroom wall clock with luminous hands and display of five minute and quarter hour intervals. It had to be effortlessly readable from the bed and the luminosity had to last through the night.

The luminous paint used on modern clocks tends to be disappointing and most will not last for a full night. We have come a long way from the days when zinc sulphide activated with radioisotopes such as radium or tritium gave good service--absolutely forbidden now! However it is now possible to obtain 'glow in the dark' powders based on rare earth doped strontium aluminate which do not need radioactivity. These powders are available in a number of colours but the green one has the best staying power and will emit light for twenty four hours after activation by natural or artificial light. The 'glow in the dark' powder far outperforms the old style zinc sulphide but the green light emitted is very similar.

The powders can be difficult to apply mainly due to their coarse nature which means that you cannot make useable paints from them and grinding impairs the light emitting property. This article shown how they can be applied in situ with cheap nail varnish which is cellulose nitrate dissolved in an acetone/amyl acetate solvent and is very similar to the 'dope' used by model aircraft enthusiasts many years ago.

Please take a look at a previous 'ible here where some of the techniques used in this article were worked up.

Step 1: You Will Need:

Glow in the Dark Powder: This is widely available from eBay and Amazon and is relatively cheap. Be sure that is is based on rare earth doped strontium aluminate and choose the green variety as this has the longest persistence and the ability to emit light for 24 hours after charging. The material used here was from Alpha Industries Incorporated.

Cheap Nail Varnish: this is a case where cheapest is best. Nail Varnish is made from a solution of cellulose nitrate in an acetone/amyl acetate solvent. You can use the integral brush or cheap artist brushes may help.

Step 2: First Get Your Clock

There are many many clocks out there! We need to be able to access the hands so if they are behind a glass then we need to know for certain that we can get behind it to work. This is not easy to tell when the clock is on display in a shop and the information may not be easy to ascertain. The clock should be reasonably cheap so that any disaster is not too disastrous. For reasons that will become apparent simple chunky hands that have a large surface area will make the job much simpler. In our case, the project was for bedroom use so silence in operation was vital--this can be the source of some anguish as in our case where one partner can hear a pin drop at three floors down. (The other is increasingly deaf!)

Our chosen clock, rather a compromise, can be seen in the picture above. It is a wall clock and quite large at twelve inches diameter which means that it can be easily read from fifteen feet away. It is fairly quiet in operation. Importantly for this project the hands are out in the open and can be worked on without removal from the clock mechanism albeit they are rather ornate but widely sold. A very important factor is the free space vertically between the two hands.We are going to apply a pad of 'glow in the dark' powder to them and the hour hand must then not foul the minute hand above as it rotates. With this particular clock there is a healthy eighth of an inch clearance.

Step 3: Deal With Simple Hands

We will go off at a tangent for the next four steps by dealing with the case where your clock has simple hands i.e. where the luminous powder can be applied directly.

In the picture above we have a simple cheap clock. It has hands made from brass like metal and can be treated simply.

Step 4: Deal With Simple Hands--Protect the Face.

Lay the clock in a tray. Nail Varnish will attack plastics and furniture to say nothing of nylons and tights.

Nail varnish gives off narcotic fumes and it is probably best to adjourn to shed or garage.

In the picture above you will see how a sheet of card in two parts has been gently slid under the hands to protect the face and to allow for the collection of excess powder.

Step 5: Deal With Simple Hands--Apply the Powder.

Lightly paint the hands with the brush from the bottle of nail varnish. When you have 'wet' all of the area, take a full brush of varnish and paint/drip the varnish on to the hands so as to create a 'pool' without it overflowing.

Now, before the varnish evaporates, spoon 'glow in the dark' powder liberally over the hands allowing the excess to overflow on to the card below. Leave to dry for several hours.

Step 6: Deal With Simple Hands--Finish

Withdraw the card with the excess of 'glow in the dark' powder. Invert the clock over a large sheet of paper and collect the excess of 'glow in the dark' powder. Save the excess powder for further use. You should now have a 'cushion' of powder plus nail varnish on the hands. Consolidate your work by giving the hands a final top coat of nail varnish.

The results can be seen in the left hand part of the composite picture above and the nocturnal effect on the right.

The simplicity of the last four steps does show the benefits of finding, if you can, a clock with simple hands.

Step 7: Deal With Difficult Hands

These hands are a most unpromising candidate for our purpose. They are very ornate and have insufficient surface area to take much 'glow in the dark' powder directly but they are widely sold. The decision was taken to make luminous strips separately and then glue these to the hands afterwards.

This will also apply where you have needle sharp hands which cannot of themselves carry much powder.

Step 8: Deal With Difficult Hands

Shown in the left hand side of the composite picture above you will see the plastic sheet that formed the top of a box of Christmas cards. The material is probably PET (Polyethylene terephthalate).

Strips were cut from the plastic to be the length of the respective arms and these are shown in the right hand side of the picture.

{Later on in the project it was found in practice that nail varnish does NOT make a truly permanent bond to PET and our cushion of luminous powder can be lifted with vigorous rubbing. My use of super glue (see later,) and subsequent varnishing means that the hands made here will probably last for the purposes of this project in the long term but those starting the project from scratch might do well to use a material such as cartridge paper, very thin card or perhaps marquetry wood. It is most important not to build up the thickness to the extent where the two hands foul each other during rotation.}

Step 9: Difficult Hands--Apply Powder to the Strips

Two rows of four pellets of Blu Tack (white) were placed on a card in a metal tray and flattened to the same height with a thick straight edge. The two strips were lightly stuck to the Blu Tack pellets as shown in the left hand side of the composite picture above.

The right hand side of the picture shows how the strips were then coated with nail varnish and an excess of luminous powder spooned on in the manner that should be becoming familiar before being left to dry.

Knock off the excess powder on to a sheet of paper and save. Apply a coat of nail varnish to consolidate the luminous layer.

Step 10: Difficult Hands--Apply the Luminous Hand Patches

The picture above shows one way of applying the hand patches. The patch to be applied can be seen loose on the clock face in the upper part of the picture. A pad of A4 printer paper has been carefully slid under the minute hand. Worked out by trial and error, the pad has just enough A4 sheets to allow this and we can now press down on the hand without damage to the mechanism.

The luminous patch can now be carefully tacked on to the clock hand with a small amount of nail varnish at each end and allowed to dry. Now take a tube of superglue and carefully apply this under the edges of the luminous patch at various points along the length. The glue will seep in under the patch due to capillary action. Allow to dry and then add a final consolidating coat of nail varnish to the hand.

The hour hand has already received the treatment.

Step 11: Make the Time Interval Markers

I resolved to put one set of markers at the quarter hour positions and a smaller set at the remaining five minute intervals.

I made 'glow in the dark' stickers as shown in a previous Instructable which can be found here. Triangular markers made from double sided sticky pads cut diagonally in half were used for the quarter hour markers and simple round sticky pads for the remaining markers. See the picture above for the basic pads which are sold for furniture protection and can be found in do-it-yourself and pound shops.

Step 12: Make the Time Interval Markers

In the picture above we see how our pads and cut down double sided sticky pads have been anointed with nail varnish and then covered with an excess of 'glow in the dark powder'.

After removal of the excess powder and the application of a consolidating final coat of varnish they are ready for use.

Step 13: Apply the Time Interval Markers

Now the rear of each sticker may be peeled and the sticker placed in position on the clock. The triangular ones are used at the quarter hour positions with the apex opposite the hypotenuse pointing inwards. The circular ones are simply placed in position at the other interval points. Once stuck in position it is difficult to move the stickers--the process may be facilitated by the use of wooden cocktail sticks.

The job is now complete.

Step 14: Some Last Thoughts

It came as a revelation to us just how effective a large luminous clock can be in the bedroom and yet this is something that is not easily available to purchase ready made.

This article should show how to judge if a given clock is suitable for this treatment and the approach has been flexible enough to allow for individual variations.

If you do have a clock that is noisy but suitable in all other respects note that it is possible to replace the whole movement with a SUPERSWEEP Non Ticking version. There are many clock movement suppliers worldwide but for useful advice see:



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    I forgot one important detail: Luminous duct tape won't glow as long.

    1 reply

    Thanks for your interest.

    The key here is how long does it glow and will it glow all night?

    I think that the products based on zinc sulphide without radioisotope activation will not and I think many products fall into this category. They are very impressive to start with especially if you expose them to a bright light but fail to deliver after an hour or so.

    Read the reviews from those who have purchased the luminous alarm clocks that are widely and cheaply available and you will detect an underlying theme of disappointment with the luminosity.

    The green variety of rare earth doped strontium aluminate really does glow all night after activation and perhaps it is the coarse nature of the product that stops its wider application--fundamentally it is not based on expensive materials.

    Regarding your point regarding duct tape I see that clear duct tape is available although I have never used it. As a suggestion it might be an idea to lay some out on a surface from which it can be peeled and then carefully spread some 'glow in the dark' powder in the central area. Then place another tape layer on top sealing your powder in. You can now peel off your combined product sandwich and deploy elsewhere.

    Nice tips about the nail polish vs superglue. For lazy builders, luminous duct tape exists, bands could be cut and put in place. Results will depend how good you are with an X-Acto!