diff --git a/examples/bases.php b/examples/bases.php
new file mode 100644
index 0000000..77f8e8f
--- /dev/null
+++ b/examples/bases.php
@@ -0,0 +1,32 @@
+<?php
+
+require_once __DIR__."/../vendor/autoload.php";
+
+use NoccyLabs\Juicer\Ingredient\Base;
+use NoccyLabs\Juicer\Ingredient\NicotineBase;
+
+printf("Apparent Specific Gravity of base mixes:\n\n");
+printf("   VG   | PG   | ASG\n");
+printf("  ------|------|------------------------\n");
+for ($pg = 0; $pg < 100; $pg += 10) {
+    $base = new Base("PG{$pg}");
+    printf("   %3d%% | %3d%% | %.4fg/mL\n", 100-$pg, $pg, $base->getSpecificGravity());
+}
+
+echo "\n\n";
+
+$asgstrength = [ 24, 20, 18, 15 ];
+$asgheader = join("", array_map(function ($s) { return sprintf("%2dmg    ", $s); } , $asgstrength));
+
+printf("Apparent Specific Gravity of nicotine bases:\n\n");
+printf("   VG   | PG   | %s\n", $asgheader);
+printf("  ------|------|-------------------------------------\n");
+for ($pg = 0; $pg < 100; $pg += 10) {
+    printf("   %3d%% | %3d%% |", 100-$pg, $pg);
+    $base = new Base("PG{$pg}");
+    foreach($asgstrength as $s) {
+        $nicbase = new NicotineBase($base, $s);
+         printf(" %6.4f ", $nicbase->getSpecificGravity());
+    }
+    printf("\n");
+}
diff --git a/src/Recipe/Recipe.php b/src/Recipe/Recipe.php
index e7189dc..be44dd5 100644
--- a/src/Recipe/Recipe.php
+++ b/src/Recipe/Recipe.php
@@ -24,39 +24,59 @@ class Recipe implements RecipeInterface
     /** @var IngredientInterface[] */
     protected $ingredients = [];
 
-    public function setRecipeName(?string $name)
+    public function setRecipeName(?string $name): Recipe
     {
         $this->name = $name;
+        return $this;
     }
 
-    public function setRecipeAuthor(?string $author)
+    public function setRecipeAuthor(?string $author): Recipe
     {
         $this->author = $author;
+        return $this;
     }
 
-    public function setTags(array $tags)
+    public function setTags(array $tags): Recipe
     {
         $this->tags = $tags;
+        return $this;
     }
 
-    public function addTag(string $tag)
+    public function addTag(string $tag): Recipe
     {
         $this->tags[] = $tag;
+        return $this;
     }
 
-    public function setDescription(?string $description)
+    public function hasTag(string $tag): bool
+    {
+        return in_array($tag, $this->tags);
+    }
+
+    public function removeTag(string $tag): Recipe
+    {
+        $this->tags = array_filter($this->tags, function ($input) use ($tag) {
+            return $input != $tag;
+        });
+        return $this;
+    }
+
+    public function setDescription(?string $description): Recipe
     {
         $this->description = $description;
+        return $this;
     }
 
-    public function addIngredient(IngredientInterface $ingredient)
+    public function addIngredient(IngredientInterface $ingredient): Recipe
     {
         $this->ingredients[] = $ingredient;
+        return $this;
     }
 
-    public function setExtra(array $extra)
+    public function setExtra(array $extra): Recipe
     {
         $this->extra = $extra;
+        return $this;
     }
 
     /**
diff --git a/tests/Recipe/RecipeTest.php b/tests/Recipe/RecipeTest.php
index 09eb0d9..ddb7ec8 100644
--- a/tests/Recipe/RecipeTest.php
+++ b/tests/Recipe/RecipeTest.php
@@ -25,4 +25,33 @@ class RecipeTest extends \PhpUnit\Framework\TestCase
         $this->assertEquals([$ingredient1, $ingredient2], $recipe->getIngredients());
     }
 
+    public function testManipulatingRecipeTags()
+    {
+        $recipe = new Recipe();
+
+        $recipe
+            ->addTag("foo")
+            ->addTag("bar");
+        
+        $this->assertCount(2, $recipe->getTags());
+        $this->assertTrue($recipe->hasTag("foo"));
+        $this->assertTrue($recipe->hasTag("bar"));
+        $recipe->removeTag("foo");
+        $this->assertCount(1, $recipe->getTags());
+        $this->assertTrue($recipe->hasTag("bar"));
+
+        $recipe->addTag("baz");
+        $this->assertCount(2, $recipe->getTags());
+        $this->assertFalse($recipe->hasTag("foo"));
+        $this->assertTrue($recipe->hasTag("bar"));
+        $this->assertTrue($recipe->hasTag("baz"));
+
+        $recipe->setTags(["baz"]);
+        $this->assertCount(1, $recipe->getTags());
+        $this->assertFalse($recipe->hasTag("foo"));
+        $this->assertFalse($recipe->hasTag("bar"));
+        $this->assertTrue($recipe->hasTag("baz"));
+
+    }
+
 }
\ No newline at end of file