Love of Science
几年前，我们开始结合我们的科学和您的艺术，以帮助您为您最喜欢的水手制作秘密情人。我们使用红外摄像头展示了访问博物馆的情人节纸牌中隐藏的消息，并带回家与他们所爱的人分享。While we can’t meet in person this year to do this activity, we can assist in making some secret messages for that special someone on Valentine’s Day! This year we are going to explore the making and use of, drumroll please, Invisible Ink!!!!
Invisible Ink
要提供一点背景，有许多不同的隐形墨水可以选择（有关其他隐形油墨的更多信息，请查看The Secret History of Invisible Ink）。我们决定选择大多数人在厨房中可以轻松访问的公式：基于酸的无形墨水。也许最常见的不可见墨水是柠檬汁，这是一种味道浓郁的水果中的高度酸性汁。从不畏惧！如果您没有柠檬或柠檬汁，则还有其他选择无形墨水的选择。
Acid sources in your kitchen Image Credits: The Mariners’ Museum and Park
柑橘类水果将大部分工作,酸味dicates an acid. (Some citrus fruits may have enough color in their juice to leave behind some color on white paper. Keep this in mind before you use them). Also, vinegar is a good option as well. If you don’t have standard vinegar you may look to your pickle jar too! Differences in the concentration of acid in these compounds make a difference in how well the ink will show when developed. It is worth trying out your acid-based ink prior to making your final secret message(s) for your favorite Mariner(s)!
Science of Paper和How This Invisible Ink Works
Invisible inks based on acids like lemon juice or vinegar actually take advantage of the chemistry of paper and the fact that it breaks down in the presence of acid. This reaction is fairly slow at room temperature, but over time the acidic breakdown of paper is what causes paper to yellow as it ages.
纸的老化还会导致“书籍气味”至少我们熟悉的一些“书籍气味”。（在尝试不同的烤箱温度时，我（Molly）开始闻到来自我厨房的香草的味道。香草（Vanilla）的主要调味化学化学品香草（Vanillin我的烤箱中的一些复制纸给了我一个相当不错的气味！）。
Back to the chemistry:
Heating up the paper speeds up the reaction of the acid with the paper. The addition of acid in a concentrated area of the paper (writing) means that this area of the paper breaks down more quickly and thus changes color more quickly.
Image Credit: The Mariners’ Museum and Park
If you happen to have an acid mixed in with a bit of sugar (see most citrus fruit juices sold as juice) you also get the benefit of the sugar in the mix that browns along with the paper. A bit of caramelization of your ink, if you will.
When We Don’tLove纸上的酸
Here we are harnessing the effects of acids in paper for good, but in most cases paper and acid are not so sweet on each other!
酸不仅将纸变成棕色时，它也使纸变得非常脆，因此在弯曲时很容易断裂。
外酸
Where does acid come from in paper? It depends! It can be added to the paper from other materials that touch it, like our “ink”. For example, iron gall ink, which was widely used for centuries, can be very acidic, and in extreme cases can cause areas of the paper to fall out! (A different kind of “invisible ink?”)
Internal Acids
酸也可以来自纸本身，具体取决于其制成的内容。大多数人知道纸来自树木，意为木材。但这并非总是如此！早期纸是用棉布和亚麻布抹布制成的。这些类型的纤维往往不会随着时间的流逝而分解那么多，因此用它们制成的纸可以保持灵活性和明亮数百年！
当1800年代初发明了造纸机时，这种做法发生了变化。新机器制作的纸如此之快，以至于实际上用完了抹布！取而代之的是，纸磨制造商开始使用木浆，该木浆自然具有较高的酸含量（也有一些化学过程用于打破有助于酸含量的木浆）。结果，1850 - 1950年之间的时期被称为“脆弱的书籍时代”，因为当时发表的许多论文迅速退化。如今，使用前对木浆进行了化学处理，因此酸性零件要么被去除或中和，从而产生较长的纸张。（要了解有关造纸的更多信息，请参见：https://blog.www.boxorats.com/2020/05/prape-and-water-friends-or-foes/）
顶部：左图显示工人通过抹布进行分类以用于造纸，右图显示了制作纸，一次是从这些抹布中制成的一张纸。（Diderot Encylopedie，巴黎：1751-1765。）底部：更现代的四缸制造机的一部分图像（c。1950）。想象一下，这台机器比上面的单个纸匠可以制造的纸更多！
The Good News
Whether the acids come from inside or outside the paper, the chemical reactions by which they break down the paper can be sped up by other factors like light, humidity, and – as we see from our invisible inks – heat! That’s why it is important to keep paper in dark, drier (humidity at ~50% RH) – aka NOT your attic! Museums have specially controlled environments for artifact storage which extends the life of paper (and other materials) by keeping these reactions at bay.
Image Credit: The Mariners’ Museum and Park
But what if the damage has already been done? Paper conservators have a couple of tricks up their sleeves when it comes to acidic paper. Sometimes, water can be used to wash out acids that have built up in the paper over time. (This is also true of your invisible ink, if you get the paper wet after you write your message, your message will wash away!) Another option is to add basic, or alkaline, chemicals to the paper to neutralize the acids and prevent them from breaking down the paper.
The Bad News
不幸的是，许多用酸性木浆制成的论文和书籍都遭受了不可逆转的损害，并且由于本文本质上是酸性的，因此无法停止降解，并且随着时间的流逝，纸张的状况会变得越来越糟。在这些情况下，重新标准（通常是通过数码摄影）是保存的最佳形式，可确保子孙后代能够获得某种形式的人工制品。
We will undoubtedly talk more about digital preservation in future blogs, but if you are interested in learning more about the topic generally check out the Library of Congress’s resource page:https://www.digitalpreservation.gov/。
Recipe for Making Your Valentine
材料
- Ink – Lemon juice (or other acid source – vinegar, fresh squeezed citrus juice. Check out the image below for options you might have in your kitchen.)
- Paper – white, or lightly colored paper. (Feel free to try colored construction or cardstock paper, it may be harder to read.)
- Writing/drawing instrument (a paintbrush works well, but feel free to experiment!)
- Heat source – oven at 400 F for two minutes (minimum) or a lit candle with adult supervision
三纸 - 左粉红色卡片纸，中间白色卡片纸，右白色打印机纸。
ACV – apple cider vinegar, vin – vinegar, wwv – white wine vinegar, lime – lime juice, lemon – lemon juice, GF – grapefruit juice (with sugar added), wine – white wine, PJ – dill pickle juice
Image Credit: The Mariners’ Museum and Park
Directions
- 用你的墨水的选择和你的写作工具choice write your message on your valentine. There are a number of options you can experiment with for either the ink or your writing tool. Have fun playing around with it!! (We had good luck with lemon juice and a paint brush).
*We recommend that you run a test first to see how your ink and paper change color with heat.*
Valentines With A Secret Message Written
- Let your ink completely dry, it should be invisible. (Some acid sources may have a little color to them. Orange or grapefruit juice may leave a slight tinge of color).
- 使用诸如预热至400 F的烤箱之类的热源或在成人监督的情况下，您可以使用蜡烛来开发消息。如果您使用蜡烛，我们建议您在水槽或浴缸中进行此操作，以防纸着火。
Text was going to say “Secrets Come Out When Things Heat Up”. Unfortunately the paper caught on fire a few times.
Image Credit: The Mariners’ Museum and Park
The oven will take a couple of minutes to develop the message. The longer it sits the darker the message, but the rest of the paper also gets darker. Using the candle you have to carefully heat the back of the paper with the flame, it takes some practice.
发表消息的情人节
- Once you have perfected how you write with invisible ink, make your Mariner’s Valentine and send it to them.
Make sure to send some helpful instructions on how they get their message!
Share your Valentines with us onFacebookortwitter使用#iamamariner!!!!
