materials for outdoor sign letters

[mark lankton]

Most of the work we do is with wood. However, we're doing a sign now that will be outdoors and I'm thinking that some type of plastic (black) would be the right stuff to cut out for the letters on our laser. The biggest letters will be 6" tall and I'm thinking 1/4" thick. We have a 40w mercury pinnacle. The letters would be mounted on a slab of Douglas fir. Any thoughts on a good solution for materials as well as mounting them (I'd like to have about a 1/16-1/8" space between the letters and the wood) would be greatly appreciated as well as suppliers. Thanks in advance.

Mark

[Larry Bratton]

Most of the work we do is with wood. However, we're doing a sign now that will be outdoors and I'm thinking that some type of plastic (black) would be the right stuff to cut out for the letters on our laser. The biggest letters will be 6" tall and I'm thinking 1/4" thick. We have a 40w mercury pinnacle. The letters would be mounted on a slab of Douglas fir. Any thoughts on a good solution for materials as well as mounting them (I'd like to have about a 1/16-1/8" space between the letters and the wood) would be greatly appreciated as well as suppliers. Thanks in advance.

Mark
Acrylic is a good outside material. Cuts on the laser very well.
I suggest that you use a very good adhesive also. I am currently working on some big wall signs that are inside and have acrylic glued to a melamine panel. Expensive, so I wanted the best adhesive I could get.
I am using IPS Weldon 45. It is recommended for gluing acrylic to metals, metal to metal, and just about anything else. I talked to IPS tech support and they said it sticks to most anything and I believe it after using it. However, the downside is that is it very expensive and requires a $200 mixing gun, but if you have reservations about glueing your letters, this stuff will make your fears disappear. Their are others I'm sure that work just as well and are cheaper too, so look around. Good luck!

[Rodne Gold]

Acrylic as mentioned as well as Black formica
Acrylic is best glued to dissimilar backgrounds with marine silicon sealant or any other likewise product. The silicon grips like crazy to the smooth surfaces and has some give in regard to expansion , pex expands a lot. Its almost impossible to remove the lettering if you use this.
The formicas can be glued using contact adhesive.
To make life easier , we actually vector outline the lettering on the substrate board if the letters are stuck on , if possible , to aid placement and registration. We often laser engrave the smaller letter that would be fiddly to cut and only laser cut the big stuff.
Stand offs are best made using 1/4 inch acrylic , make disks and stick em on the back of the letters and stick these to the boards , alternatively you can use clear acrylic and cut the same set of letters but with a countor "inline" making em smaller than the letters themselves and glue both on the board , IE a black letter with a clear letter behind (this will assure you dont have letters falling off.
We would normally use the disc method for small stand offs , and a another system of posts fort big ones (like when the customer wants 1+ cm of the letters standing proud)

[John Keeton]

I have not done any sign work, but have played with wood for many years. You are using dissimilar materials with different expansion/contraction properties. While Douglas fir normally has a low expansion/contraction property, many environmental factors could come into play. In a 6 inch span, any movement could affect the bond between the wood and the acrylic.

I would encourage you to use some sort of mechanical fastener as opposed to an adhesive unless you use a substance that never totally hardens and remains flexible to a degree. Not having had the need, I wouldn't be able to contribute a suggestion on that.

[Rodne Gold]

The marine silicon sealant fits that bill , it never gets hard , same stuff they use to seal the glass sides of fishtanks etc.nIf he uses mechanical , he has to make slightly oversize holes to account for perspex expansion. Actually its more a visual thing with the perspex than fear of it falling off , tho thats a concern , perspex is flat and shiny and any warp whatsoever in it , especially the 3mm stuff shows like crazy.
If its for outdoors , I think you need to seriously weatherproof the wooden backing board. We use hard oily woods for backboards , like Balau or rhodesian teak etc , and just oil it with a mixture of boiled linseed and turps. Dunno if thats the best way of doing it ? Im not all that clued up re wood finishing. We did try various outdoor varnishes , but find they degrade over time and its hell on earth to remove them , the sign has to come down. The linseed/turps thing can be reapplied on site or the owner can just do it himself every so often. Generally the wood boards we do are mounts for brass plates etc , so they can bear the cost of using the woods we do as its quite expensive signage.
We often use wood grain formicas tho , on some cheaper weatherproof substrate for larger "wood effect " signage.

[Doug Bergstrom]

We cut and mount acrylic letters all the time to wood, brick, pvc etc. See some of our other post for examples. With brick and wood we use an acrylic block on the back of the letter attached wtih Weld-on and post mount this in to the sign base with silicone adhesive. Silicone will not harden and stay flexible. We have signs attached to roofs with large letter with nothing but silicone and they hold a snow load here in VT. For the sign itseld we no longer use any wood in our outdoor signs because they just do not hold up here with our extreme weather. We make everything now out of either PVC, avrylic, alumabond or sign foam with great success.

[Clyde Baumwell]

Lexel is an excellent silicone, flexible adhesive for indoor and outdoor use. Not found in Home Depot or Lowes but in specialty or hardware stores.

[mark lankton]

Thanks for all the great replies. The sign is for the local American Legion Hall. The Doug fir was donated and while our company will get paid we're trying to keep costs to a minimum. You know, one of those "good guy" projects, hopefully we won't lose both our shirts and pants. I like the idea of stacking the acrylic to get a little shadow line. What type of acrylic should we use? Extruded, etc ? Thanks again, this is a great fount of information. I'll almost sound like I know what I'm doing when I talk to the boss today.

Mark

[Frank Corker]

If you are engraving it, cast acrylic is probably the best, extruded leaves a very subtle impact in comparison

[Larry Bratton]

I have not done any sign work, but have played with wood for many years. You are using dissimilar materials with different expansion/contraction properties. While Douglas fir normally has a low expansion/contraction property, many environmental factors could come into play. In a 6 inch span, any movement could affect the bond between the wood and the acrylic.

I would encourage you to use some sort of mechanical fastener as opposed to an adhesive unless you use a substance that never totally hardens and remains flexible to a degree. Not having had the need, I wouldn't be able to contribute a suggestion on that.
I disagree with mechanical fastening for acrylic. If it can't move at all, it will buckle in the sun. Black would be particularly bad because it absorbs heat and take it from someone that has tried it in the sun,,you don't want to do that. It's UGLY what it does.

[John Keeton]

Larry

I admit ignorance on the acrylic - or sign building generally. But, in joining two different wood species, with different expansion properties, one always allows for movement with slotted holes. I honestly don't know if that would work in this application not knowing the layout. My concern was simply that if the letters were adhered to the wood with an adhesive that was not elastic, then one of two things happen, the letters come off, or distort. Beyond that, I'm out of my league!!