Black Granite vs Black Marble

[Terry Swift]

Why do suppliers like to mess with our minds? Like mouths, everybody has an opinion on a given subject; so why should the debate between granite and marble be any different.

Company A out there says they don't sell much granite; especially smaller pieces for indoor usage like for photo plaques, etc. - which they say black marble is a better choice and backed up by "most" laser manufacturers buy marble versus granite for indoor usage. Company B does sell the smaller granite pieces and they actively engage in saying granite is a perfect stone to use anywhere - both indoors and out. I have not used Company A's products yet; so not sure if their claim is a valid one. As for Company B's products, their granite is okay; but their quality control suffers some.

Just trying to get a general consensus on granite over marble for general usage and when it come to color filling.

I appreciate everyone's input.

[Mike Mackenzie]

Marble is a softer stone and you can achieve some depth whereas granite is much harder and nearly impossible to get depth.

Granite weathers much better than marble thus inside and outside comments.

Marble also gets better gray scale tones because it contains no speckles unlike granite.

Marble is usually higher in price and harder to get than granite.

Marble is more forgiving with power settings than granite is.

These are the differences that I have noticed working with both materials.

[Tom Bull]

You can get incredible detail with marble as compared to granite.

[Paul Perkinson]

We've done a lot of both for several years now and I would basically agree with the "marble inside, granite outside" mantra. The veinless black marble has a sharp, beautiful contrast every time and we would use only that if it would stand up to outdoor conditions. It won't. For one thing, it gets a light "milky" look over the entire black portion of the stone after a pretty short time outside. The only other negative we have to always keep an eye on is the difference between pieces. We normally buy 100 to 300 or more square feet at a time and hope that helps minimize this effect. As long as you are just selling a single piece it doesn't matter, but if you are selling a mural of several pieces there will sometimes be a significant difference in the engraved/non-engraved contrast from one (or more) of the pieces to the rest of the pieces in the mural.

There are a few occasions where we had to redo some of the mural because it was so noticeable. Given that we use a 4' x 8' machine for this and normally do a mural as one file, this is not a welcome situation. Still - the marble provides a wonderful detail and contrast that makes a semi-rare situation such as this worthwhile.

Absolute black granite can also be fantastic to work with, but it has a much larger "grain" than the marble does. It is actually basalt rather than granite, but that almost falls in the "so what - who cares" category as long as it works. Lack of contrast or sharpness are usually because of the size and/or composition of some of the granules making up the basalt (for one, it seems like a higher quartz content is good indicator of less than great results). We've done it enough now that we can pretty much always tell by looking at the stone prior to engraving whether it will do well or not. You can usually get a better idea by looking at the unpolished back of the stone than by looking at the polished face because the individual components of the stone are easier to pick out prior to being polished. That is even more true if the quarry or distributor has used an enhancing sealer on the stone face after polishing.

For what it's worth, if we are doing a photo-quality engraving we keep the power backed off some compared to when we are doing line drawings or text only. Too easy to "over burn" the details out of the photo if not careful, but the text/line drawings usually can gain a bit of contrast from the extra energy without loss of crispness. If the job has both (common) we do the photo portion(s) on a separate file and run each of the files with their appropriate settings.

Funny (not ha ha) thing is that it is just as likely to be the cheapest abs black you can find that will give up the best engraving. When we do monuments or memorials we either arrange to provide the stone ourselves or make sure the provider is very aware of how much the specific stone can affect the final outcome. We've got a couple of samples - one that looks great and the other that looks fair - that we show to whoever is supplying the stone and point out the differences is size and make-up of the composite pieces in the stone. The file and settings used for both pieces were the same. They almost always get it right away and keep us involved in the stone selection after that.

So I guess I'm just being extremely long winded (gee, that's new!) to say that I pretty much agree with them. For inside, marble would be my first choice always, but with the understanding that some absolute black granite (basalt), if very carefully chosen, is virtually as good and has the benefit of taking far less laser energy to engrave to a crisp contrast than marble. For outside applications, we will NOT use marble without a waiver signed by the customer. It is worded in no uncertain manner that marble does not weather well outdoors and the responsibility for that rests entirely on them.

Don't think that's really what you were hoping to hear, but that's just one set of lips, er opinion.

[Terry Swift]

Thanks all.

I'm going to try the marble, as it is only about a $1 or 2 higher per piece than the granite I was getting. If the results are better - I'd be crazy not to go that way; even if I have to charge a couple dollars more. Granite is frustration to me; but I do so much of it and if it is not engraved good, then color filling becomes a real problem. I hope marble works better there too or maybe to a point where color fill isn't even necessary - which would save me tons.

Most of my work lately has been with 5x7 ovals and 6" circles for Police and Fire Departments to put their badges and logo's on them. Some of my pieces actually went into their "Wall of Fame," which floored me. Now they want me to engrave Glocks, Shotguns, etc. for the Wall as well as personal. Gets a bit scary doing some of this stuff; but they like what I do at a decent price - so more business flows my way.

[Paul Perkinson]

I think you wil like the results after you dial in the right settings. As stated elsewhere, I would expect higher power or lower speed or some combination thereof as compared to abs blk granite.

An almost completely random thought struck me upon seeing who the work is for. If you happen to find a market for shapes other than hearts, circles, and ovals you may want to take a look at something on the order of a Gemini saw. Cuts through marble like butter and can cut some pretty intricate shapes (such as a revolver gripped in a hand and pointing at you, or just the weapon in profile) with no problem. Add a little engraving to provide the detail lines and they look really good. If you haven't seen the tool, they are ring saws. Takes a couple of fairly large orders to justify them unless you're a "toy" collector. Honestly, we got one before we really should have, but it turned out ok. One nice thing about living in Orlando is all the shows and conventions here which means you can often pick up a machine that was used only for demos during the 1 to 5 days of the show for as little as half the normal price. One guy can zip around most any outline in no time. Between that tool, for stone work, and a CNC router, we can now do most work in-house that we used to have to send out for waterjet cutting.

We never use any white color fill when using marble and we're pretty picky. I'm sure you already know this, but if you want to do color (as opposed to using white) color fill, we find that oil pastel "crayons" from an art store or any art web site such as Dick Blick, do a great job. Everybody probably has their own little "secrets" about the exact process, but a bit of experimentation can provide fairly spectacular results. We use them for artwork mostly, but selective highlighting, such as on a seal, can also really dress up a citation or such. Perceived value seems to go much higher considering we really don't get much pushback about charging quite a bit more for it. I admit that it's not a good business move, but when work is to be presented to individual military members or civilian first-responders, we seem to develop amnesia about how much the up-charge is supposed to be.

If you may be doing weapons in the future (receivers I presume) you might consider heeding some of the good, previous advice here on the Creek about limiting your liabilities with a written waiver or similar protective legal instrument. Most of the weapons work we do is for US soldiers who purchase the parts and put together their own weapons to take to combat. Many of them like a 10" barrel for house-to-house or urban fighting and Uncle Sam doesn't provide that. I have them sign the waiver, but if anything went wrong I would replace the entire receiver if necessary; even if I could legally get by with less. The point is, that would be my choice, not my obligation.

If you already have all this stuff under control please just disregard my diarrhea of the fingers (it's a disease that even age hasn't been able to cure). Best of luck with it. Those guys deserve the best and it sounds like you are doing a great job of providing that.

Now you can see why I don't come on the forum much any more. Waste too much of my time and yours. Sincere apologies. Hello. My name is Paul and I'm a talkaholic.

[Dan Hintz]

Terry,

As usual, this thread is worthless without pics

[Paul Perkinson]

Sorry, hardly any pictures on this computer. The centaur is from a test we were doing with 3cm granite frames for painted 1 cm black veinless marble. This particular one was a tropic brown granite frame made for a 9" x 12" tile if I remember right. The centaur was only 8" x 10" so you can see under her skirt a bit, but it was what was laying around at the time. This particular version of her was a reject piece because of some horizontal banding so the color was added rather quickly just to evaluate whether to continue with the concept. Still, it gives a decent idea I hope.

The lighthouse was a 2' x 3' practice mural for a new person. That's why the pieces were just roughly pushed together for the picture. We did not go any further with this one. Had it been going out the door there would have been some cleanup and then highlighting done and the lines between pieces would have almost not been seen by the time it was set and framed.

Hopefully, with a little imagination, you can even see with small files of these 2 pieces that it is not terribly difficult with a bit of practice and some trial and error. I'm best at the error part.

I cannot for the life of me find any pictures of those revolver pieces on this drive but they really did come out well. Perfect canvases for 2nd amendment statements. You know, the "When guns are outlawed, only outlaws will have guns" with the revolver pointed right at you.

I did find an example of where we used less power on an image than on text so that we didn't blow out the image, but got the best contrast for the text. For whatever reason I can't seem to add it now to this post so I'll just do another post for that in a minute.

[Paul Perkinson]

Not sure you will be able to see the difference, but the emblems of the U.S. Service branches would have had details washed out if we used as much power on them as we did the text. Conversely, the text would not have popped out like it does if we had used the lower power we used on the images. From our experience, this is the norm with absolute black granite. Your mileage may vary. None of the engraving was enhanced with coloring or stain or anything. It is just as it came off the machine (well, ok, it was cleaned and we go out each Veteran's Day to clean it again).

Unfortunately, I do not have a good example of a piece that has both an image and text mixed in together available. That is where we would create 2 files and run them separately with different settings. Obviously, on this piece we did not have to do that because they were on different sides of the memorial. Couldn't help but include the one with the reflection of the flag. It doesn't help you visualize at all, but I do love that picture.

[Paul Perkinson]

Terry,
I came in to work early to find, and post, a bunch of pictures showing the contrast between black marble and absolute black granite as well as "good" absolute black granite versus "not good" absolute black granite. We have sample pieces that we show all the time so I figured I could just take some new photos if I couldn't find what I wanted right away.

The Creek was always a great place that felt like home, but I've hardly had time to sign in - maybe 3 or 4 times in the last year is all I've managed. Before that, over the last several years, I've picked up some great tips here and hoped there would eventually be a way for me to give back a little. Having entirely different equipment than nearly everyone else, there are many subjects I can't contribute to. Your question was one that was equipment neutral and something that I have many hundreds of hours of experience in so I thought it a great chance to jump in. Not unusual for me, I let my enthusiasm get carried away and even started giving tips and thoughts that were far off the simple question you asked. For going so far astray I do apologize. I meant well, I assure you, but I do carry on.

It used to be that people on the Creek were eager to help each other out and I'm fairly sure they did not have to offer photographic evidence to support each piece of advice. Anyone who disagreed simply said so. Always in a nice manner and frequently with some good natured and humorous kidding (for some reason, Frank comes to mind about here). I certainly remember seeing photos of people's work, but my poor memory had it that those were most often supplied as a "hey, look at what I've been working on" or "what do you think caused this?" type of situation. I had not been around enough to learn that things had changed to the point where a person's opinion was useless if not accompanied by the proper photographic documentation.

The impact of that finally occurred to me on the way to work - yes I'm a bit slow - and I realized that I really do not have the necessary time to contribute in this manner. So I apologize for the worthless advice I posted from home on Sunday and wish you the best in your endeavors.

[Scott Shepherd]

Paul, I think you misunderstood the post that offended you. It was done in jest, saying "Hey, that sounds like something you do a lot of, care to share some photos?", rather than how it might have read at the time.

There's a nudge nudge, wink wink thing that goes on that says if you don't share photos, then it didn't happen. It's usually done in humor, because someone's posted something excellent and didn't post any photos, so it gets us wanting me.

I really appreciate your knowledge and photos on this thread. That's some beautiful work. I haven't contributed more to this thread, as I feel like your knowledge is far beyond anything I can offer.

[Richard Rumancik]

Paul, your comments are most valuable with or without pictures. I know it takes a long time to write a good post and your information is appreciated. I think the comment regarding lack of photos was directed to Terry, not you. I suppose it could have been said a little differently. Please don't hesitate to post without pics as you obviously have a lot of knowledge on this subject.

[Dan Hintz]

Paul,

Indeed, my post was directed at Terry, not you... and as others have noted, it's a "net-approved", tongue-in-cheek method of asking posters to show everyone pictures of their handy work so they can gloat. It's never used in a nasty way (at least not that I'm aware of).

Besides, you already posted pics, so you're safe

[Paul Perkinson]

Well, I feel a proper fool. Not to put my heart too far out on my sleeve, I have 3 people very dear to me in one way or another that don't have much time left on this side of eternity. I realize, most of the time, that nothing could be more natural and their companionship has only been on loan to me from the beginning. I further realize, most of the time, that there may very well be several BILLION people who would just love to trade their troubles for mine. I have to keep a cheery attitude to buoy the spirit of family & friends (that's what happens when you outlive the rest of the males in the family tree - people figure you either killed the others off, so they're scared of you, or they figure you know something they don't [you don't] so they tend to take their cues from you. Apparently, it seems, I decided to become thin-skinned and take it out on what I perceive to be another "family" of whom I'm a member.

Thank you for straightening me out - that's something else family and only true friends do. I would say, "Please accept my apology", but I don't want anyone to use up valuable time and space to reply to my foolishness after I have already sidetracked the discussions we all love, and completely hijacked poor Terry's thread.

I will continue to post whenever I get a chance and my skin will not be so thin again. We spent at least 2 years floundering around when we first started and maybe I can put together some general things we learned (to do or not to do - that is the question) complete with some photos to illustrate the points. I know several people have done that to various degrees in various areas (I think Rodne was the first) but we do enough different types of things here that we might be able to help newbies avoid a mine or two. In many areas we have little to no experience so I won't try to tell more than I know (I hope).

I make no promises that I will be able to do this - I just took on teaching robotics and rocketry to a homeschooling group in my "spare" time - but I do promise to keep it in mind and try. In the mean time, may I throw down the challenge for others to do the same. For example - I'm going to pick on Dan because that signature line makes him an obvious choice - could Dan put together a primer on how to use LEDs most effectively for edge lighting. It could include when to tape off what edges of the acrylic or other main media with what type of material depending on the application or "look" desired. It could contain factors to consider for whether the electronics should be powered by AC or a DC wall wart or batteries or solar or one of those as primary with another for backup. It could discuss the virtues of SMT strips versus individual LEDs; which would most likely lead to at least a high-level discussion of resistor selection, parallel versus series configurations, how many mcd's from each LED (and color) do you think are necessary to properly illuminate common thicknesses of acrylic or other materials for a certain length or width, etc. Does the refractive index of the material need to be a certain minimum or maximum and do most cast and extruded acrylics a Creeker would normally get fall within that tolerance? Is it ever necessary to use a polarizing film or reflective film to trap or redirect the light? What PCM control units are best to control color-changing LED circuits in various configurations and color scheme desires - which come ready to go and what options are there from that up to using a PIM or arduino or similar programming tool to have total control over color options? It could go on and on, but those are just some ideas off the top of the head.

I absolutely have no authority to speak for Keith or anyone else, but my personal opinion is that if someone were to put in that much work on such a project that could benefit so many members, well perhaps they could be allowed to offer some of those components for sale or at least mention their web site in the tutorial/primer so people could go to look for some of these things. They wouldn't be forced to go there, but as long as the prices were competitive I would imagine many would. Could be a great service to everyone. I have not been to Dan's website and I also don't know if there is someone else on the Creek that sells LED components so I hope I am not stepping on toes. If there is a conflict of that nature, then perhaps Keith would be willing to have a sticky that references tutorials/how-to's/primers/equipment add-ons and such as this done by any member. Anyone interested could check out the information from those listed and make up their own minds about the quality of the information and from whom (if anyone) they wanted to buy. Perhaps members could "be the first to rate" the information they found in these pearls of wisdom.

If these ideas have already been raised and rejected then I'm sorry to have taken up time with old business. I should have done a search first and admit that I did not. If they haven't been raised, they may or may not be worth consideration. They are just random thoughts during lunch. The Creek is overflowing its banks with volumes of useful, sometimes vital, information and I think new people would just love to have a simplified source to go to for certain topics, knowing they can get additional, in-depth data through a search. It's not just new people really. It can also be someone who's been around for quite a while but is now curious about what it would take to add a new service to their business that they see a need for in their area. Shoot, it could even be member contributions kinda like Wikipedia.

Sorry, Mods. Just realized that not only have I ranged so far off topic as to warrant a call to the Guiness people (beer or records clan, either one), but also that my brilliant little brain cramp would likely cause you all a massive amount of work that I'm sure you don't need. Having gone through the exercise of typing it, however, I'm going ahead with it and you can use the mighty power contained in the role of editor to obliterate it at your pleasure. Apologies yet again for long-windedness. I can't find a 12 step program for it, but I am aware that I need one.

[Dan Hintz]

I'm going to pick on Dan because that signature line makes him an obvious choice - could Dan put together a primer on how to use LEDs most effectively for edge lighting.

It's probably not convenient for you being in Florida and all, but you really should consider attending Angus's ShopBot days (one coming up September 11th). At last year's meet I held a 30-45 minute discussion on just such a topic, with some examples on hand for edge lighting, flood lighting, etc. This year (if I can find the time to finish it) I will be holding a discussion on how to easily create grayscale height-map images for routing and lasering 2.5D objects.